Underwater environment

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Great Barrier Reef, Australia Great Barrier Reef snorkeling 18.jpg
Great Barrier Reef, Australia

An underwater environment is a environment of, and immersed in, liquid water in a natural or artificial feature (called a body of water), such as an ocean, sea, lake, pond, reservoir, river, canal, or aquifer. Some characteristics of the underwater environment are universal, but many depend on the local situation.

Contents

Liquid water has been present on Earth for most of the history of the planet. The underwater environment is thought to be the place of the origin of life on Earth, and it remains the ecological region most critical to the support of life and the natural habitat of the majority of living organisms. Several branches of science are dedicated to the study of this environment or specific parts or aspects of it.

A number of human activities are conducted in the more accessible parts of the underwater environment. These include research, underwater diving for work or recreation, and underwater warfare with submarines. It is hostile to humans in many ways and often inaccessible, and therefore relatively little explored.

Extent

The world ocean is the most visible part of Earth from space. BlueMarble-2001-2002.jpg
The world ocean is the most visible part of Earth from space.

Three quarters of the planet Earth are covered by water. Most of the planet's solid surface is abyssal plain, at depths between 4,000 and 5,500 metres (13,100 and 18,000 ft) below the surface of the oceans. The solid surface location on the planet closest to the center of the geoid is the Challenger Deep, located in the Mariana Trench at a depth of 10,924 metres (35,840 ft). There is a smaller part of the surface covered by bodies of fresh water and a large volume of underground water in aquifers. The underwater environment is hostile to humans in many ways and therefore little explored. It can be mapped by sonar, or more directly explored via manned, remotely operated, or autonomous submersibles. The ocean floors have been surveyed via sonar to at least a coarse resolution; particularly-strategic areas have been mapped in detail, to assist in navigating and detecting submarines, though the resulting maps may be classified.[ citation needed ]

Oceans and seas

Clouds over the Atlantic Ocean Clouds over the Atlantic Ocean.jpg
Clouds over the Atlantic Ocean

An ocean is a body of water that composes much of a planet's hydrosphere. [1] On Earth, an ocean is one of the major conventional divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. [2] [3] The word "ocean" is often used interchangeably with "sea" in American English. Strictly speaking, a sea is a body of water (generally a division of the world ocean) partly or fully enclosed by land, [4] though "the sea" refers also to the oceans.

Saline water covers approximately 361,000,000 km2 (139,000,000 sq mi) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of Earth's surface and 90% of the Earth's biosphere. [5] The ocean contains 97% of Earth's water, and oceanographers have stated that less than 5% of the World Ocean has been explored. [5] The total volume is approximately 1.35 billion cubic kilometers (320 million cu mi) with an average depth of nearly 3,700 meters (12,100 ft). [6] [7] [8]

Lakes, ponds, and rivers

Samur River in Azerbaijan - In the natural landscape Reka Samur.jpg
Samur River in Azerbaijan – In the natural landscape

A lake is an area filled with water, localized in a basin, that is surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. [9] Lakes lie on land and are not part of the ocean, and therefore are distinct from lagoons, and are also larger and deeper than ponds, though there are no official or scientific definitions. [10] Lakes can be contrasted with rivers or streams, which are usually flowing. Most lakes are fed and drained by rivers and streams. Natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the last ice age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them. Many lakes are artificial and are constructed for industrial or agricultural use, for hydro-electric power generation or domestic water supply, or for aesthetic, recreational purposes, or other activities.

A pond is an area filled with water, either natural or artificial, that is smaller than a lake. [11] It may arise naturally in floodplains as part of a river system, or be a somewhat isolated depression (such as a kettle, vernal pool, or prairie pothole). It may contain shallow water with marsh and aquatic plants and animals. [12] Ponds are frequently man-made or expanded beyond their original depth and bounds. Among their many uses, ponds provide water for agriculture and livestock, aid in habitat restoration, serve as fish hatcheries, are components of landscape architecture, may store thermal energy as solar ponds, and treat wastewater as treatment ponds. Ponds may be fresh, saltwater, or brackish.

A river is a natural flowing watercourse, usually freshwater, flowing under the influence of gravity on ocean, lake, another river, or into the ground. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, [13] Rivers are part of the hydrological cycle; water generally collects in a river from precipitation in a drainage basin from surface runoff and other sources such as groundwater recharge, springs, and the release of stored water in natural ice and snow. Potamology is the scientific study of rivers, while limnology is the study of inland waters in general.

Subterranean water

Typical aquifer cross-section Aquifer en.svg
Typical aquifer cross-section
Diving in a flooded cave JB CAVE.png
Diving in a flooded cave

An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. If an impermeable layer overlies the aquifer, pressure could cause it to become a confined aquifer.

Aquifers may be classified as porous or karst, where a porous aquifer contains the water in the spaces between the grains of a loose sediment or rock (typically sand or sandstone), while a karst aquifer contains water mainly in relatively large voids in relatively impermeable rock, such as limestone or dolomite. [14]

Water filled caves can be classified as active and relict: active caves have water flowing through them; relict caves do not, though water may be retained in them. Types of active caves include inflow caves ("into which a stream sinks"), outflow caves ("from which a stream emerges"), and through caves ("traversed by a stream"). [15]

Artificial bodies of water

A reservoir is, most commonly, an enlarged natural or artificial lake, pond or impoundment created using a dam or lock to store water. Reservoirs can be created in a number of ways, including controlling a watercourse that drains an existing body of water, interrupting a watercourse to form an embayment within it, through excavation, or building retaining walls or levees. Canals are artificial waterways which may have dams and locks that create reservoirs of low speed current flow.

Physical characteristics

Water is a transparent, tasteless, odorless, and nearly colorless chemical substance. Its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of H2O at standard ambient temperature and pressure. Water at the surface of the Earth moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Water seldom exists in a pure form, it almost always contains dissolved substances, and usually other matter in suspension.

Density

Density of ice and water as a function of temperature Density of ice and water (en).svg
Density of ice and water as a function of temperature

The density of water is about 1 gram per cubic centimetre (62 lb/cu ft) The density varies with temperature, but not linearly: as the temperature increases, the density rises to a peak at 3.98 °C (39.16 °F) and then decreases; this is unusual. [16] Regular, hexagonal ice is also less dense than liquid water—upon freezing, the density of water decreases by about 9%. [17] These effects are due to the reduction of thermal motion with cooling, which allows water molecules to form more hydrogen bonds that prevent the molecules from coming close to each other. [16] While below 4 °C the breakage of hydrogen bonds due to heating allows water molecules to pack closer despite the increase in the thermal motion (which tends to expand a liquid), above 4 °C water expands as the temperature increases. [16] Water near the boiling point is about 4% less dense than water at 4 °C (39 °F). [17] [lower-alpha 1]

Temperature distribution in a lake in summer and winter Anomalous expansion of water Summer Winter.svg
Temperature distribution in a lake in summer and winter

The unusual density curve and lower density of ice than of water is vital to life—if water were most dense at the freezing point, then in winter the very cold water at the surface of lakes and other water bodies would sink, the lake could freeze from the bottom up, and all life in them would be killed. [17] Furthermore, given that water is a good thermal insulator (due to its heat capacity), some frozen lakes might not completely thaw in summer. [17] The layer of ice that floats on top insulates the water below. [18] Water at about 4 °C (39 °F) also sinks to the bottom, thus keeping the temperature of the water at the bottom constant (see diagram). [17]

The density of sea water depends on the dissolved salt content as well as the temperature. Ice still floats in the oceans, otherwise they would freeze from the bottom up. The salt content lowers the freezing point by about 1.9 °C and lowers the temperature of the density maximum of water to the fresh water freezing point at 0 °C. [19] This is why, in ocean water, the downward convection of colder water is not blocked by an expansion of water as it becomes colder near the freezing point. The oceans' cold water near the freezing point continues to sink. So creatures that live at the bottom of cold oceans like the Arctic Ocean generally live in water 4 °C colder than at the bottom of frozen-over fresh water lakes and rivers.

As the surface of sea water begins to freeze (at −1.9 °C for salinity 3.5%) the ice that forms is essentially salt-free, with about the same density as freshwater ice. [19] This ice floats on the surface, and the salt that is "frozen out" adds to the salinity and density of the sea water just below it, in a process known as brine rejection . This denser salt water sinks by convection. This produces essentially freshwater ice at −1.9 °C on the surface. [19] On a large scale, the process of brine rejection and sinking cold salty water results in ocean currents forming to transport such water away from the Poles, leading to a global system of currents called the thermohaline circulation.

Pressure

The density of water causes ambient pressures that increase dramatically with depth. The atmospheric pressure at the surface is 14.7 pounds per square inch or around 100 kPa. A comparable hydrostatic pressure occurs at a depth of only 10 metres (33 ft) (9.8 metres (32 ft) for sea water). Thus, at about 10 m below the surface, the water exerts twice the pressure (2 atmospheres or 200 kPa) as air at surface level.

Buoyancy

Any object immersed in water is subjected to a buoyant force that counters the force of gravity, appearing to make the object less heavy. If the overall density of the object exceeds the density of water, the object sinks. If the overall density is less than the density of water, the object rises until it floats on the surface.

Penetration of light

Note the bluish cast given to objects in this underwater photo of pillow lava (NOAA). Nur05018-Pillow lavas off Hawaii.jpg
Note the bluish cast given to objects in this underwater photo of pillow lava (NOAA).

With increasing depth underwater, sunlight is absorbed, and the amount of visible light diminishes. Because absorption is greater for long wavelengths (red end of the visible spectrum) than for short wavelengths (blue end of the visible spectrum), the colour spectrum is rapidly altered with increasing depth. White objects at the surface appear bluish underwater, and red objects appear dark, even black. Although light penetration will be less if water is turbid, in the very clear water of the open ocean less than 25% of the surface light reaches a depth of 10 m (33 feet). At 100 m (330 ft) the light present from the sun is normally about 0.5% of that at the surface.[ citation needed ]

The euphotic depth is the depth at which light intensity falls to 1% of the value at the surface. This depth is dependent upon water clarity, being only a few metres underwater in a turbid estuary, but may reach up to 200 metres in the open ocean. At the euphotic depth, plants (such as phytoplankton) have no net energy gain from photosynthesis and thus cannot grow.

Temperature

There are three layers of ocean temperature: the surface layer, the thermocline, and the deep ocean. The average temperature of surface layer is about 17 °C. About 90% of ocean's water is below the thermocline in the deep ocean, where most of the water is below 4 °C. [20]

There are temperature anomalies at active volcanic sites and hydrothermal vents, where deep-water temperatures can significantly exceed 100 °C.

Thermal conductivity

Water conducts heat around 25 times more efficiently than air. Hypothermia, a potentially fatal condition, occurs when the human body's core temperature falls below 35 °C. Insulating the body's warmth from water is the main purpose of diving suits and exposure suits when used in water temperatures below 25 °C.

Acoustic properties

Sound is transmitted about 4.3 times faster in water (1,484 m/s in fresh water) than in air (343 m/s). The human brain can determine the direction of sound in air by detecting small differences in the time it takes for sound waves in air to reach each of the two ears. For these reasons, divers find it difficult to determine the direction of sound underwater. Some animals have adapted to this difference and many use sound to navigate underwater.

Ecosystems

An estuary mouth and coastal waters, part of an aquatic ecosystem Estuary-mouth.jpg
An estuary mouth and coastal waters, part of an aquatic ecosystem

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. [21]

Marine ecosystems are the largest of Earth's aquatic ecosystems and are distinguished by waters that have a high salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply [22] [23] and 90% of habitable space on Earth. [24] Marine ecosystems include nearshore systems, such as the salt marshes, mudflats, seagrass meadows, mangroves, rocky intertidal systems and coral reefs. They also extend from the coast to include offshore systems, such as the surface ocean, pelagic ocean waters, the deep sea, oceanic hydrothermal vents, and the sea floor. Marine ecosystems are characterized by the biological community of organisms that they are associated with and their physical environment. As the world ocean is the principal component of Earth's hydrosphere, it is integral to life, forms part of the carbon cycle, and influences climate and weather patterns. The World Ocean is the habitat of 230,000 known species, but because much of it is unexplored, the number of species that exist in the ocean is much larger, possibly over two million. [25]

Freshwater ecosystems include lakes and ponds, rivers, streams, springs, aquifers, bogs, and wetlands. They have a lower salt content than marine ecosystems. Freshwater habitats can be classified by different factors, including temperature, light penetration, nutrients, and vegetation. Freshwater ecosystems can be divided into lentic ecosystems (still water) and lotic ecosystems (flowing water). [26]

Aquatic ecosystems are characterised by the limitation on ambient lighting due to absorption by the water itself and by dissolved and suspended matter in the water column, and by the support provided by buoyancy. Nutrients usable by plants are dissolved in the water, making them easily available. However, the interaction of light absorption by water, matter and living organisms themselves leads to very different light and light spectrum conditions depending on the respective ecosystem and its water depth. This affects photosynthesis and the ecology of plants and phytoplankton. [27] Outside the euphotic zone, photosynthesis cannot occur and life must use other sources of energy than sunlight.

Humans

Although a number of human activities are conducted underwater—such as research, underwater diving for work or recreation, and underwater warfare with submarines, the underwater environment is hostile to humans in many ways and therefore little explored.

An immediate obstacle to human activity under water is that human lungs cannot naturally function in this environment. Unlike the gills of fish, human lungs are adapted to the exchange of gases at atmospheric pressure. Any penetration into the underwater environment for more than a few minutes requires artificial aids to maintain life.

For solid and liquid tissues like bone, muscle and blood, the high ambient pressure is not much of a problem; but it is a problem for any gas-filled spaces like the mouth, ears, paranasal sinuses and lungs. This is because the gas in those spaces is much more compressible than the solids and liquids, and reduces in volume much more when under pressure and so does not provide those spaces with support against the higher outside pressure. Even at a depth of 8 ft (2.4 m) underwater, an inability to equalize air pressure in the middle ear with outside water pressure can cause pain, and the tympanic membrane (eardrum) can rupture at depths under 10 ft (3 m). The danger of pressure damage is greatest in shallow water because the ratio of pressure change is greatest near the surface of the water. The raised pressure also affects the solution of breathing gases in the tissues over time, and can lead to a range of adverse effects, such as inert gas narcosis, and oxygen toxicity. Decompression must be controlled to avoid bubble formation in the tissues and the consequent symptoms of decompression sickness.

With a few exceptions, the underwater environment tends to cool the unprotected human body. This heat loss will generally lead to hypothermia eventually.

Hazards

There are several classes of hazards to humans inherent to the underwater environment.

Ambient pressure diving

Tektite I underwater habitat with ambient pressure divers using scuba Tektite I exterior.jpg
Tektite I underwater habitat with ambient pressure divers using scuba

In ambient pressure diving, the diver is directly exposed to the pressure of the surrounding water. The ambient pressure diver may dive on breath-hold, or use breathing apparatus for scuba diving or surface-supplied diving, and the saturation diving technique reduces the risk of decompression sickness (DCS) after long-duration deep dives. Immersion in water and exposure to cold water and high pressure have physiological effects on the diver which limit the depths and duration possible in ambient pressure diving. Breath-hold endurance is a severe limitation, and breathing at high ambient pressure adds further complications, both directly and indirectly. Technological solutions have been developed which can greatly extend depth and duration of human ambient pressure dives, and allow useful work to be done underwater. [28]

Atmospheric pressure diving

The Newtsuit has fully articulated, rotary joints in the arms and legs. These provide great mobility, while remaining largely unaffected by high pressures. Newtsuit atmospheric diving suit.jpg
The Newtsuit has fully articulated, rotary joints in the arms and legs. These provide great mobility, while remaining largely unaffected by high pressures.

A diver can be isolated from the ambient pressure by using an atmospheric diving suit (ADS), which is a small one-person articulated anthropomorphic submersible which resembles a suit of armour, with elaborate pressure resisting joints to allow articulation while maintaining an internal pressure of one atmosphere. An ADS can be used for relatively deep dives of up to 2,300 feet (700 m) for many hours, and eliminates the majority of significant physiological dangers associated with deep diving; the occupant need not decompress, there is no need for special gas mixtures, nor is there danger of decompression sickness or nitrogen narcosis, and the diver is effectively isolated from most aquatic organisms. [29] Divers do not even need to be skilled swimmers, but mobility and dexterity are significantly degraded.

Submersibles and submarines

A submersible is a small watercraft designed to operate underwater. The term submersible is often used to differentiate from other underwater vessels known as submarines, in that a submarine is a fully autonomous craft, capable of renewing its own power and breathing air, whereas a submersible is usually supported by a surface vessel, platform, shore team or sometimes a larger submarine. There are many types of submersibles, including both manned and unmanned craft, otherwise known as remotely operated vehicles or ROVs. [30]

Remotely operated or autonomous vehicles

ROV working on a subsea structure ROV working on a subsea structure.jpg
ROV working on a subsea structure
Pluto Plus AUV for underwater mine identification and destruction. From Norwegian minehunter KNM Hinnoy MiniU.jpg
Pluto Plus AUV for underwater mine identification and destruction. From Norwegian minehunter KNM Hinnøy

Remotely operated underwater vehicles and autonomous underwater vehicles are part of a larger group of undersea systems known as unmanned underwater vehicles. ROVs are unoccupied, usually highly maneuverable, and operated by a crew either aboard a vessel/floating platform or on proximate land. They are linked to a host ship by a neutrally buoyant tether, or a load-carrying umbilical cable is used along with a tether management system (TMS). The umbilical cable contains a group of electrical conductors and fiber optics that carry electric power, video, and data signals between the operator and the TMS. Where used, the TMS then relays the signals and power for the ROV down the tether cable. Once at the ROV, the electric power is distributed between the components of the ROV. In high-power applications, most of the electric power drives a high-power electric motor which drives a hydraulic pump for propulsion and to power equipment. Most ROVs are equipped with at least a video camera and lights. Additional equipment is commonly added to expand the vehicle's capabilities. Autonomous underwater vehicles (AUVs) are robots that travel underwater without requiring input from an operator. Underwater gliders are a subclass of AUVs. [31]

Sciences

See also

Related Research Articles

<span class="mw-page-title-main">Deep diving</span> Underwater diving to a depth beyond the norm accepted by the associated community

Deep diving is underwater diving to a depth beyond the norm accepted by the associated community. In some cases this is a prescribed limit established by an authority, while in others it is associated with a level of certification or training, and it may vary depending on whether the diving is recreational, technical or commercial. Nitrogen narcosis becomes a hazard below 30 metres (98 ft) and hypoxic breathing gas is required below 60 metres (200 ft) to lessen the risk of oxygen toxicity.

Diving physics, or the physics of underwater diving is the basic aspects of physics which describe the effects of the underwater environment on the underwater diver and their equipment, and the effects of blending, compressing, and storing breathing gas mixtures, and supplying them for use at ambient pressure. These effects are mostly consequences of immersion in water, the hydrostatic pressure of depth and the effects of pressure and temperature on breathing gases. An understanding of the physics behind is useful when considering the physiological effects of diving, breathing gas planning and management, diver buoyancy control and trim, and the hazards and risks of diving.

<span class="mw-page-title-main">Saturation diving</span> Diving decompression technique

Saturation diving is diving for periods long enough to bring all tissues into equilibrium with the partial pressures of the inert components of the breathing gas used. It is a diving mode that reduces the number of decompressions divers working at great depths must undergo by only decompressing divers once at the end of the diving operation, which may last days to weeks, having them remain under pressure for the whole period. A diver breathing pressurized gas accumulates dissolved inert gas used in the breathing mixture to dilute the oxygen to a non-toxic level in the tissues, which can cause decompression sickness if permitted to come out of solution within the body tissues; hence, returning to the surface safely requires lengthy decompression so that the inert gases can be eliminated via the lungs. Once the dissolved gases in a diver's tissues reach the saturation point, however, decompression time does not increase with further exposure, as no more inert gas is accumulated.

<span class="mw-page-title-main">Submersible</span> Small watercraft able to navigate under water

A submersible is an underwater vehicle which needs to be transported and supported by a larger watercraft or platform. This distinguishes submersibles from submarines, which are self-supporting and capable of prolonged independent operation at sea.

<span class="mw-page-title-main">Depth gauge</span> Instrument that indicates depth below a reference surface

A depth gauge is an instrument for measuring depth below a vertical reference surface. They include depth gauges for underwater diving and similar applications. A diving depth gauge is a pressure gauge that displays the equivalent depth below the free surface in water. The relationship between depth and pressure is linear and accurate enough for most practical purposes, and for many purposes, such as diving, it is actually the pressure that is important. It is a piece of diving equipment used by underwater divers, submarines and submersibles.

<span class="mw-page-title-main">Diving bell</span> Chamber for transporting divers vertically through the water

A diving bell is a rigid chamber used to transport divers from the surface to depth and back in open water, usually for the purpose of performing underwater work. The most common types are the open-bottomed wet bell and the closed bell, which can maintain an internal pressure greater than the external ambient. Diving bells are usually suspended by a cable, and lifted and lowered by a winch from a surface support platform. Unlike a submersible, the diving bell is not designed to move under the control of its occupants, or to operate independently of its launch and recovery system.

<span class="mw-page-title-main">Diving support vessel</span> Ship used as a floating base for professional diving projects

A diving support vessel is a ship that is used as a floating base for professional diving projects. Basic requirements are the ability to keep station accurately and reliably throughout a diving operation, often in close proximity to drilling or production platforms, for positioning to degrade slowly enough in deteriorating conditions to recover divers without excessive risk, and to carry the necessary support equipment for the mode of diving to be used.

<span class="mw-page-title-main">Atmospheric diving suit</span> Articulated pressure resistant anthropomorphic housing for an underwater diver

An atmospheric diving suit (ADS) is a small one-person articulated submersible which resembles a suit of armour, with elaborate pressure joints to allow articulation while maintaining an internal pressure of one atmosphere. An ADS can enable diving at depths of up to 700 metres (2,300 ft) for many hours by eliminating the majority of significant physiological dangers associated with deep diving. The occupant of an ADS does not need to decompress, and there is no need for special breathing gas mixtures, so there is little danger of decompression sickness or nitrogen narcosis when the ADS is functioning properly. An ADS can permit less skilled swimmers to complete deep dives, albeit at the expense of dexterity.

<span class="mw-page-title-main">Underwater habitat</span> Human habitable underwater enclosure filled with breathable gas

Underwater habitats are underwater structures in which people can live for extended periods and carry out most of the basic human functions of a 24-hour day, such as working, resting, eating, attending to personal hygiene, and sleeping. In this context, 'habitat' is generally used in a narrow sense to mean the interior and immediate exterior of the structure and its fixtures, but not its surrounding marine environment. Most early underwater habitats lacked regenerative systems for air, water, food, electricity, and other resources. However, some underwater habitats allow for these resources to be delivered using pipes, or generated within the habitat, rather than manually delivered.

<span class="mw-page-title-main">Diving chamber</span> Hyperbaric pressure vessel for human occupation used in diving operations

A diving chamber is a vessel for human occupation, which may have an entrance that can be sealed to hold an internal pressure significantly higher than ambient pressure, a pressurised gas system to control the internal pressure, and a supply of breathing gas for the occupants.

<span class="mw-page-title-main">Deep-sea exploration</span> Investigation of ocean conditions beyond the continental shelf

Deep-sea exploration is the investigation of physical, chemical, and biological conditions on the ocean waters and sea bed beyond the continental shelf, for scientific or commercial purposes. Deep-sea exploration is an aspect of underwater exploration and is considered a relatively recent human activity compared to the other areas of geophysical research, as the deeper depths of the sea have been investigated only during comparatively recent years. The ocean depths still remain a largely unexplored part of the Earth, and form a relatively undiscovered domain.

<span class="mw-page-title-main">Dive planning</span> The process of planning an underwater diving operation

Dive planning is the process of planning an underwater diving operation. The purpose of dive planning is to increase the probability that a dive will be completed safely and the goals achieved. Some form of planning is done for most underwater dives, but the complexity and detail considered may vary enormously.

Diving hazards are the agents or situations that pose a threat to the underwater diver or their equipment. Divers operate in an environment for which the human body is not well suited. They face special physical and health risks when they go underwater or use high pressure breathing gas. The consequences of diving incidents range from merely annoying to rapidly fatal, and the result often depends on the equipment, skill, response and fitness of the diver and diving team. The classes of hazards include the aquatic environment, the use of breathing equipment in an underwater environment, exposure to a pressurised environment and pressure changes, particularly pressure changes during descent and ascent, and breathing gases at high ambient pressure. Diving equipment other than breathing apparatus is usually reliable, but has been known to fail, and loss of buoyancy control or thermal protection can be a major burden which may lead to more serious problems. There are also hazards of the specific diving environment, and hazards related to access to and egress from the water, which vary from place to place, and may also vary with time. Hazards inherent in the diver include pre-existing physiological and psychological conditions and the personal behaviour and competence of the individual. For those pursuing other activities while diving, there are additional hazards of task loading, of the dive task and of special equipment associated with the task.

<span class="mw-page-title-main">Outline of underwater diving</span> Hierarchical outline list of articles related to underwater diving

The following outline is provided as an overview of and topical guide to underwater diving:

<span class="mw-page-title-main">Index of underwater diving</span> Alphabetical listing of underwater diving related topics

The following index is provided as an overview of and topical guide to underwater diving:

The science of underwater diving includes those concepts which are useful for understanding the underwater environment in which diving takes place, and its influence on the diver. It includes aspects of physics, physiology and oceanography. The practice of scientific work while diving is known as Scientific diving. These topics are covered to a greater or lesser extent in diver training programs, on the principle that understanding the concepts may allow the diver to avoid problems and deal with them more effectively when they cannot be avoided.

Diving support equipment is the equipment used to facilitate a diving operation. It is either not taken into the water during the dive, such as the gas panel and compressor, or is not integral to the actual diving, being there to make the dive easier or safer, such as a surface decompression chamber. Some equipment, like a diving stage, is not easily categorised as diving or support equipment, and may be considered as either.

<span class="mw-page-title-main">Underwater exploration</span> Investigating or traveling around underwater for the purpose of discovery

Underwater exploration is the exploration of any underwater environment, either by direct observation by the explorer, or by remote observation and measurement under the direction of the investigators. Systematic, targeted exploration is the most effective method to increase understanding of the ocean and other underwater regions, so they can be effectively managed, conserved, regulated, and their resources discovered, accessed, and used. Less than 10% of the ocean has been mapped in any detail, less has been visually observed, and the total diversity of life and distribution of populations is similarly obscure.

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  16. 1 2 3 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 625. ISBN   978-0-08-037941-8.
  17. 1 2 3 4 5 Perlman, Howard. "Water Density". The USGS Water Science School. Retrieved 2016-06-03.
  18. ↑ Zumdahl, Steven S.; Zumdahl, Susan A. (2013). Chemistry (9th ed.). Cengage Learning. p. 493. ISBN   978-1-13-361109-7.
  19. 1 2 3 "Can the ocean freeze?". National Ocean Service. National Oceanic and Atmospheric Administration. Retrieved 2016-06-09.
  20. ↑ "Temperature of Ocean Water". Windows to the Universe. National Earth Science Teachers Association (NESTA).
  21. ↑ Alexander, David E. (1 May 1999). Encyclopedia of Environmental Science. Springer. ISBN   0-412-74050-8.
  22. ↑ "Oceanic Institute". www.oceanicinstitute.org. Archived from the original on 2019-01-03. Retrieved 2018-12-01.
  23. ↑ "Ocean Habitats and Information". 2017-01-05. Archived from the original on April 1, 2017. Retrieved 2018-12-01.
  24. ↑ "Facts and figures on marine biodiversity | United Nations Educational, Scientific and Cultural Organization". www.unesco.org. Retrieved 2018-12-01.
  25. ↑ Drogin, Bob (August 2, 2009). "Mapping an ocean of species". Los Angeles Times. Retrieved August 18, 2009.
  26. ↑ Wetzel, Robert, G. (2001). Limnology : lake and river ecosystems (3rd ed.). San Diego: Academic Press. ISBN   978-0127447605. OCLC   46393244.{{cite book}}: CS1 maint: multiple names: authors list (link)
  27. ↑ Hintz, Nils Hendrik; Schulze, Brian; Wacker, Alexander; Striebel, Maren (March 2022). "Ecological impacts of photosynthetic light harvesting in changing aquatic environments: A systematic literature map". Ecology and Evolution. 12 (3): e8753. doi:10.1002/ece3.8753. ISSN   2045-7758. PMC   8939368 . PMID   35356568.
  28. ↑ Kot, Jacek (2011). Educational and Training Standards for Physicians in Diving and Hyperbaric Medicine (PDF). Kiel, Germany: Joint Educational Subcommittee of the European Committee for Hyperbaric Medicine (ECHM) and the European Diving Technical Committee (EDTC).
  29. ↑ "WASP Specifications" (PDF). Archived from the original (PDF) on 3 March 2014. Retrieved 27 February 2014.
  30. ↑ "Submersible". The Canadian Encyclopedia. 2011. Archived from the original on 2017-12-04. Retrieved 2019-08-09.. The Canadian Encyclopedia. F.J. Chambers 02/07/2006 "Cyrus Albert Birge - the Canadian Encyclopedia". Archived from the original on March 15, 2012. Retrieved 2011-10-20.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  31. ↑ "Remotely Operated Vehicle Design and Function". Maritime About. Archived from the original on 1 July 2016. Retrieved 4 June 2016.

Footnotes

  1. ↑ (1-0.95865/1.00000) × 100% = 4.135%
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