Open-water diving

Last updated November 27, 2024

Open water diving is underwater diving in an open water environment, where the diver has unrestricted access by way of a direct vertical ascent to the breathable air of the atmosphere. Other environmental hazards may exist which do not affect the classification. Open water diving implies that if a problem arises, the diver can directly ascend vertically to the atmosphere to breathe air, so it is also understood that, with this restriction, a staged decompression obligation is incompatible with open water diving, though it does not affect classification of the environment. This meaning is implied in the certifications titled Open Water Diver and variations thereof.

Open water environment

In underwater diving, open water is unrestricted water such as a sea, lake, river, or flooded quarry. It is a contradistinction to an overhead environment, where there is a physical barrier to direct vertical ascent to the surface, and to a flooded confined space where there may not be enough room to maneuver freely. In open water the diver has direct vertical access to the surface of the water in contact with the Earth's atmosphere.^[1]

Environments which by definition are not open water include overhead environments, and diving in these is called Penetration diving. This may involve entering caves or wrecks, or diving under ice or the hull of a large ship. In some contexts the lack of a decompression obligation is considered a necessary condition for classification of a dive as an open water dive, as a decompression obligation is a procedural and safety restriction on immediate ascent to the surface, but this does not affect the classification of the venue as open water.

Swim-throughs – the recreational diving term for arches and short, clear, tunnels where the natural light can be seen at the far end, and there is enough clearance that it is theoretically possible for the diver to pass through the narrowest point without contact with the sides, bottom or ceiling, are technically an overhead environment, but this is often overlooked by divers as there is no risk of getting lost inside, and the risk of entrapment is generally low.

Divers progress from learning diving skills in confined or benign water such as a swimming pool to practicing skills in open water in which the environment is not restricted to a small, controlled locality and depth, with conditions more typical of a natural body of water which might be used by divers,^[2] and the range of hazards and associated risk is significantly expanded.^[3] In this context confined water and benign water are special cases of open water, as they comply with the more general condition of unobstructed access to the surface.

Some recreational diver certification agencies use a variation on this term in the title of their entry level diver certification. Open Water Diver certification implies that the diver is competent to dive in unrestricted water, with various constraints regarding the conditions, and particularly that their competence is limited to diving in open water with free access to the surface.^[4]^[5]

There are a few variations of open water environments with more specific names. There are also a number of named diving environments which are usually also open water environments.

Open ocean

The extreme case of open water is the deep open ocean, where the bottom is at a depth which is irrelevant to the diver as there would be no chance of surviving long enough to reach it. Open oceanic water is often remarkably clear, but this is not always the case. There is no natural visual reference for depth in the open ocean, and depth monitoring and control is critically important to diver safety.

Blue-water diving

Blue-water diving is done in mid-water where the bottom is out of sight of the diver and there may be no fixed visual reference. It is done by scientific divers for direct observation and sampling of pelagic organisms and particulate matter, particularly the gelatinous zoo-plankton that are fragile and transparent, making them relatively inaccessible by other methods,^[6] and by recreational divers for observation and photography of a range of organisms not easily seen in inshore waters.

The techniques of blue-water diving have been developed over the years to suit the conditions and address the hazards of an environment which is functionally bottomless, and has no fixed visible positional references. The diver who is focused on small organisms or instruments at close range is likely to have diminished awareness of depth, buoyancy, current, surge, other divers, large organisms, and even the direction to the surface.^[6]

An accepted procedure for scientific blue-water collection diving with several working divers, is to tether the working divers to a central hub connected to a surface platform, and to have an in-water safety diver attend the hub. The tethers pass through fairleads at the hub and are tensioned by a weight at the end, which keeps slack out of the line and thereby reduces the risk of entanglement, and prevents the end of the line from passing through the fairlead. The tether serves to limit the distance a diver can move away from the hub, which is typically fastened to a substantial downline supported by a large buoy at the surface, and kept vertical by a weight. The float at the surface allows the divers to move freely in the water column within the constraint of the tether, and drift with the current. The tethers also allow rope signals between the safety diver and the working divers. The surface platform, generally a small boat, may be tethered to the buoy, and if there is sufficient wind to make this a problem a parachute sea anchor can be deployed to minimise drift. Windage will generally position the buoy and boat downwind of the parachute. The other end of the tether is clipped to the diver's harness or buoyancy compensator by some form of quick-release shackle.^[6] These procedures and equipment can also be used at night.

If a sea anchor is deployed to limit drift, it must be kept clear of the divers to minimise the risk of entanglement, and it should be buoyed to prevent sinking in a calm. The sea anchor cable should be buoyant line for the same reason. Blue-water diving operations are constrained by water and weather conditions, including wind, sea state, current strength, visibility, and the presence of aggressive predators.^[6]

Black-water diving

Black-water diving is mid-water diving at night, particularly on a moonless night. The environment is referred to as black-water .^[7]^[8] The term black-water may also be used to refer to diving in zero visibility, or in sewage. Christopher Newbert, author of Within a Rainbow Sea, (1984) is credited as an early black-water diver.^[9] In his book, he describes solo offshore night dives to depths of up to 150 feet (46 m).^[10] Black-water diving is often done as a photographic opportunity for recreational divers as there can be a wide range of plankton that would not often be seen by day or closer inshore.^[11] This is known as blackwater photography.^[12]

Weighted downlines are commonly used to provide a stable vertical reference. These may be tied to the boat or supported by a buoy. Each diver may be attached to a downline using a shorter tether to ensure that divers do not go too far from the boat or too deep.^[11] The downline may be marked with lights to indicate depth and to attract mobile organisms.^[10] A wide range of animal life may be seen, including many species that spend the daylight hours at depths below those accessible to ambient pressure divers, and migrate vertically through the water column on a diurnal cycle.^[9] Many of these are bioluminescent or translucent or both.^[10]

The boat moves differently from the divers and the divers move differently from the plankton, making it necessary to work to get a position from which there will be enough time to frame and take photos of the drifting subjects. The boat will drift under the influence of current and wind, while the divers and plankton will drift with the current. If there is wind the boat will drag the downlines, and if tethered to the buoy, it will drag the buoy and divers attached. If divers swim ahead of the towing action, they will have a short time to drift with the plankton and take photos until the slack in the line has been taken up, at which point the plankton will be left behind.^[11] This drift problem can be reduced by setting a parachute anchor, which will reduce wind drift to a negligible amount. The divers should stay clear of the entanglement hazard of the parachute suspension lines.^[7]

Confined water

At the other extreme from the open ocean, confined water is open water where it is not possible to inadvertently stray outside the designated area due to physical barriers. Usually this also refers to an area of known low risk and minimal hazard – benign water.

The term is often used to refer to a swimming pool or tank where initial skills training of divers takes place, which is both confined and benign. The Queensland government defines confined water for recreational diving purposes as "Water which offers pool-like conditions, good visibility, and water which is shallow enough so that all divers can stand up with their heads well clear of the water".^[13] Other definitions do not require such shallow depth, but may have a depth restriction.

Confined water has some of the characteristics of benign water, in that it is not possible to accidentally stray from the environment, but although some usages of the term confined water imply benign conditions, that meaning is not inherent in the term, as water in a confined space may logically be referred to as confined water, and such confined water may contain significant hazards.^{[ citation needed ]}

Benign water

Benign water is open water with very low risk and no unknown hazards, where it is unlikely or impossible for a diver to accidentally stray to an area of higher risk. Some definitions add a depth limit and that the water must also be confined.^[14]^[15]

Benign conditions are environments of low risk, where it is extremely unlikely or impossible for the diver to get lost or entrapped, or be exposed to hazards other than the basic underwater environment. These conditions are suitable for initial training in the critical survival skills, and include swimming pools, training tanks, aquarium tanks and some shallow and protected shoreline areas.^[14]

Related Research Articles

<span class="mw-page-title-main">Drift diving</span> Scuba diving where the diver is intentionally transported by the water flow

Drift diving is a type of scuba diving where the diver is transported by the water movement caused by the tide, an ocean current or in a river. The choice whether to drift dive depends on the purpose of the dive, and whether there is an option. At some sites there is almost always a current running, and at others the strength and direction of water movement may vary with the tide, or other driving forces, like wind or recent rainfall. At some sites there may be considerable variation in visibility and underwater life activity based on the speed and direction of flow.

<span class="mw-page-title-main">Night diving</span> Underwater diving during the hours of darkness

Night diving is underwater diving done during the hours of darkness. It frequently refers specifically to recreational diving which takes place in darkness. The diver can experience a different underwater environment at night, because many marine animals are nocturnal.

Recreational diver training is the process of developing knowledge and understanding of the basic principles, and the skills and procedures for the use of scuba equipment so that the diver is able to dive for recreational purposes with acceptable risk using the type of equipment and in similar conditions to those experienced during training.

<span class="mw-page-title-main">Surface marker buoy</span> Buoy towed by a scuba diver to indicate the divers position

A surface marker buoy, SMB, dive float or simply a blob is a buoy used by scuba divers, at the end of a line from the diver, intended to indicate the diver's position to people at the surface while the diver is underwater. Two kinds are used; one (SMB) is towed for the whole dive, and indicates the position of the dive group throughout the dive, and the other, a delayed surface marker buoy, DSMB or decompression buoy, is deployed towards the end of the dive as a signal to the surface that the divers have started to ascend, and where they are going to surface. Both types can also function as a depth reference for controlling speed of ascent and accurately maintaining depth at decompression stops. Surface marker buoys are also used by freedivers in open water, to indicate the approximate position of the diver when submerged. They may also be used to support a catch bag or fish stringer by underwater hunters and collectors. A DSMB is considered by recreational scuba divers and service providers to be a highly important item of safety equipment, yet its use is not part of the entry level recreational diver training for all training agencies, and there are significant hazards associated with incompetent use.

A diving shot line, shot line, or diving shot, a type of downline or descending line, is an item of diving equipment consisting of a ballast weight, a line and a buoy. The weight is dropped on the dive site. The line connects the weight and the buoy and is used by divers to as a visual and tactile reference to move between the surface and the dive site more safely and more easily, and as a controlled position for in-water staged decompression stops. It may also be used to physically control rate of descent and ascent, particularly by surface-supplied divers.

A dive boat is a boat that recreational divers or professional scuba divers use to reach a dive site which they could not conveniently reach by swimming from the shore. Dive boats may be propelled by wind or muscle power, but are usually powered by internal combustion engines. Some features, like convenient access from the water, are common to all dive boats, while others depend on the specific application or region where they are used. The vessel may be extensively modified to make it fit for purpose, or may be used without much adaptation if it is already usable.

Diver rescue, usually following an accident, is the process of avoiding or limiting further exposure to diving hazards and bringing a diver to a place of safety. A safe place generally means a place where the diver cannot drown, such as a boat or dry land, where first aid can be administered and from which professional medical treatment can be sought. In the context of surface supplied diving, the place of safety for a diver with a decompression obligation is often the diving bell.

Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving, an ambiguous term with several possible meanings, depending on context. Immersion in water and exposure to high ambient pressure have physiological effects that limit the depths and duration possible in ambient pressure diving. Humans are not physiologically and anatomically well-adapted to the environmental conditions of diving, and various equipment has been developed to extend the depth and duration of human dives, and allow different types of work to be done.

Diving equipment, or underwater diving equipment, is equipment used by underwater divers to make diving activities possible, easier, safer and/or more comfortable. This may be equipment primarily intended for this purpose, or equipment intended for other purposes which is found to be suitable for diving use.

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.

Scuba skills are skills required to dive safely using self-contained underwater breathing apparatus, known as a scuba set. Most of these skills are relevant to both open-circuit scuba and rebreather scuba, and many also apply to surface-supplied diving. Some scuba skills, which are critical to divers' safety, may require more practice than standard recreational training provides to achieve reliable competence.

There are several categories of decompression equipment used to help divers decompress, which is the process required to allow divers to return to the surface safely after spending time underwater at higher ambient pressures.

Diving safety is the aspect of underwater diving operations and activities concerned with the safety of the participants. The safety of underwater diving depends on four factors: the environment, the equipment, behaviour of the individual diver and performance of the dive team. The underwater environment can impose severe physical and psychological stress on a diver, and is mostly beyond the diver's control. Equipment is used to operate underwater for anything beyond very short periods, and the reliable function of some of the equipment is critical to even short-term survival. Other equipment allows the diver to operate in relative comfort and efficiency, or to remain healthy over the longer term. The performance of the individual diver depends on learned skills, many of which are not intuitive, and the performance of the team depends on competence, communication, attention and common goals.

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

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.

Wall diving is underwater diving alongside a near vertical face, usually an underwater cliff. It is a type of reef diving popular among recreational divers for the biodiversity of the benthic community on the one side with a pelagic community on the other, and useful in scientific diving when assessing biodiversity of a region. No special training is required, but good buoyancy control skills are necessary for safety. Wall dive sites vary considerably in depth, and many are suitable for drift diving when a moderate current flows along the wall.

In underwater diving, a downline is a piece of substantial cordage running from a point at the surface to the underwater workplace, and kept under some tension. It can be used as a guideline for divers descending or ascending, for depth control in blue-water diving, and as a guide for transfer of tools and equipment between surface and diver by sliding them along the downline at the end of a messenger line. A shotline is a special case of downline which uses a heavy weight at the bottom and a float at the top. A jackstay is a more lateral equivalent, that commonly follows a surface, and will not usually allow materials transfer without a messenger line from the destination end.

Low impact diving is recreational scuba diving that is intended to minimise environmental impact by using techniques and procedures that reduce the adverse effects on the environment to the minimum that is reasonably practicable for the situation. To a large extent this is achieved by avoiding contact with sensitive reef life, but it also applies to diving on historical wrecks and in caves with delicate rock formations. It is in the interests of diving tourism service providers to help protect the condition of the dive sites on which their businesses rely. They can contribute by encouraging and teaching low impact diving and following best-practice procedures for diving in sensitive areas. Low impact diving training has been shown to be effective in reducing diver contact with the bottom, the most common cause of reef damage.

The underwater diving environment, or just diving environment is the natural or artificial surroundings in which a dive is done. It is usually underwater, but professional diving is sometimes done in other liquids. Underwater diving is the human practice of voluntarily descending below the surface of the water to interact with the surroundings, for various recreational or occupational reasons, but the concept of diving also legally extends to immersion in other liquids, and exposure to other hyperbaric pressurised environments.

References

↑ "Section 2". Australian Standard AS2815.3-1992, Training and certification of occupational divers, Part 3: Air diving to 50m (2nd ed.). Homebush, New South Wales: Standards Australia. 1992. p. 9. ISBN 0 7262 7631 6.
↑ "General Standards and Procedures Guide". PADI Instructor Manual (Rev. 1/10 ed.). Professional Association of Diving Instructors. 2010. p. 17.
↑ Class IV Training Standard (Revision 5 ed.). South African Department of Labour. October 2007.
↑ "Open Water Diver". Professional Association of Diving Instructors. Archived from the original on 1 October 2018. Retrieved 4 October 2013.
↑ "Open Water Diver & Scuba Diver". Scuba Schools International. Archived from the original on 4 October 2013. Retrieved 4 October 2013.
1 2 3 4 Haddock, Stephen H.D.; Heine, John N. (2005). Scientific Blue-Water Diving (PDF). California Sea Grant College Program. Archived from the original (PDF) on 25 March 2016. Retrieved 23 November 2018.
1 2 Bartick, Mike (Spring 2017). "Blackwater Diving". Alert Diver. Divers Alert Network. Archived from the original on 7 November 2019. Retrieved 7 November 2019.
↑ "All you'll ever need to know about Blackwater Diving!". info@indigoscuba.com. Archived from the original on 7 November 2019. Retrieved 7 November 2019.
1 2 Hurley, Becca (6 November 2018). "Battle of the Blackwater Guides". Archived from the original on 3 January 2021. Retrieved 7 November 2019.
1 2 3 Hayward, Tom (5 August 2015). "Florida's Black Water Diving". xray-mag.com. Archived from the original on 7 November 2019. Retrieved 7 October 2019.
1 2 3 Milisen, Jeffrey. "Photo Tips for Blackwater Diving". Archived from the original on 7 November 2019. Retrieved 7 November 2019.
↑ Olsen, Erik (30 March 2021). "The Ocean's Youngest Monsters Are Ready for Glamour Shots". The New York Times . Archived from the original on 3 April 2021. Retrieved 3 April 2021.
↑ Staff (2 December 2011). "Recreational Diving, Recreational Technical Diving and Snorkelling Code of Practice 2011" (PDF). Queensland Government Gazette. The State of Queensland (Department of Justice and Attorney-General). Archived from the original (PDF) on 21 January 2017. Retrieved 25 April 2017.
1 2 Diving Advisory Board (2007). Code of Practice for Diving in Benign Conditions, version 0 7 (PDF). Pretoria: South African Department of Labour. Archived from the original (PDF) on 9 January 2017. Retrieved 6 November 2016.
↑ "Diving Regulations 2009". Occupational Health and Safety Act 85 of 1993 – Regulations and Notices – Government Notice R41. Pretoria: Government Printer. Archived from the original on 4 November 2016. Retrieved 3 November 2016– via Southern African Legal Information Institute.

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[AS2815.3-1992-1] "Section 2". Australian Standard AS2815.3-1992, Training and certification of occupational divers, Part 3: Air diving to 50m (2nd ed.). Homebush, New South Wales: Standards Australia. 1992. p. 9. ISBN 0 7262 7631 6.

[PADI_Manual_2010-2] "General Standards and Procedures Guide". PADI Instructor Manual (Rev. 1/10 ed.). Professional Association of Diving Instructors. 2010. p. 17.

[Class_IV_Training_Standard-3] Class IV Training Standard (Revision 5 ed.). South African Department of Labour. October 2007.

[PADI-4] "Open Water Diver". Professional Association of Diving Instructors. Archived from the original on 1 October 2018. Retrieved 4 October 2013.

[SSI-5] "Open Water Diver & Scuba Diver". Scuba Schools International. Archived from the original on 4 October 2013. Retrieved 4 October 2013.

[Haddock_and_Heine-6] 1 2 3 4 Haddock, Stephen H.D.; Heine, John N. (2005). Scientific Blue-Water Diving (PDF). California Sea Grant College Program. Archived from the original (PDF) on 25 March 2016. Retrieved 23 November 2018.

[Black-water-7] 1 2 Bartick, Mike (Spring 2017). "Blackwater Diving". Alert Diver. Divers Alert Network. Archived from the original on 7 November 2019. Retrieved 7 November 2019.

[Indigo-8] "All you'll ever need to know about Blackwater Diving!". info@indigoscuba.com. Archived from the original on 7 November 2019. Retrieved 7 November 2019.

[Sport_Diver-9] 1 2 Hurley, Becca (6 November 2018). "Battle of the Blackwater Guides". Archived from the original on 3 January 2021. Retrieved 7 November 2019.

[X-ray-10] 1 2 3 Hayward, Tom (5 August 2015). "Florida's Black Water Diving". xray-mag.com. Archived from the original on 7 November 2019. Retrieved 7 October 2019.

[UPG-11] 1 2 3 Milisen, Jeffrey. "Photo Tips for Blackwater Diving". Archived from the original on 7 November 2019. Retrieved 7 November 2019.

[20210330NYTimes-12] Olsen, Erik (30 March 2021). "The Ocean's Youngest Monsters Are Ready for Glamour Shots". The New York Times . Archived from the original on 3 April 2021. Retrieved 3 April 2021.

[Qld_CoP_rec_diving-13] Staff (2 December 2011). "Recreational Diving, Recreational Technical Diving and Snorkelling Code of Practice 2011" (PDF). Queensland Government Gazette. The State of Queensland (Department of Justice and Attorney-General). Archived from the original (PDF) on 21 January 2017. Retrieved 25 April 2017.

[Benign_CoP-14] 1 2 Diving Advisory Board (2007). Code of Practice for Diving in Benign Conditions, version 0 7 (PDF). Pretoria: South African Department of Labour. Archived from the original (PDF) on 9 January 2017. Retrieved 6 November 2016.

[DR_2009-15] "Diving Regulations 2009". Occupational Health and Safety Act 85 of 1993 – Regulations and Notices – Government Notice R41. Pretoria: Government Printer. Archived from the original on 4 November 2016. Retrieved 3 November 2016– via Southern African Legal Information Institute.

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