Penetration diving

Last updated August 08, 2024

An overhead or penetration diving environment is where the diver enters a space from which there is no direct, purely vertical ascent to the safety of breathable atmosphere at the surface. Cave diving, wreck diving, ice diving and diving inside or under other natural or artificial underwater structures or enclosures are examples. The restriction on direct ascent increases the risk of diving under an overhead, and this is usually addressed by adaptations of procedures and use of equipment such as redundant breathing gas sources and guide lines to indicate the route to the exit.^[1]^[2]^[3]

There are some applications where scuba diving is appropriate and surface-supplied diving is not, and other where the converse is true. In other applications either may be appropriate, and the mode is chosen to suit the specific circumstances. In all cases risk is managed by appropriate planning, skills, training and choice of equipment.

Environments

Penetration diving is also known as diving in overhead environments, which is a class of confinement which restricts the diver from free vertical access to the surface. An overhead environment may also be a confined space, in which the diver is restricted in their ability to maneuver, and is roughly the opposite of open water. Confinement can influence diver safety and the ability of the diver to perform the required task. Some types of confinement improve safety by limiting the ability of the diver to move into higher risk areas, others limit the ability of the diver to maneuver, to perform the task of the dive, or to escape to a place of safety in an emergency. The usual types of recreational penetration diving are cave diving, cavern diving, ice diving and wreck penetration diving. Professional divers may also penetrate culverts, intakes such as penstocks, sewers, and under floating ships. An overhead may be as minor as an overhang, a topographical feature which is open to at least one side, but obstructed overhead, and deep enough for a diver to be under the overhang, or as severe as a major restriction deep inside a cave or wreck. A restriction is a space through which it is possible for a diver to pass with some difficulty due to a lack of space. A minor restriction is too small for two divers to swim through together, a major restriction requires the diver to remove some equipment to fit through.^[4] A swim-through is an arch, lintel, or short, clear tunnel that has sufficient space to allow a diver to swim through and where the light of the opening at the far end is visible through the hole. It is technically an overhead environment, but one often entered by divers with only open water certification, if the risk of entrapment appears to be very low. Diving under moored ships, usually for inspection, maintenance and repair, or incidentally, when diving from one is also considered penetration diving if the ship is large. In some cases the gap between the ship and the bottom or the jetty or dock can be quite small and the visibility may be poor. Fatal accidents have occurred when a diver has run out of air trying to find the way out from under a large flat-bottomed vessel in low visibility.

Cave diving

Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other cave users. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave-diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave-diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave-diving and cavern-diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water surface may also be specified.^[5]

Equipment, procedures, and the requisite skills have been developed to reduce the risk of becoming lost in a flooded cave, and consequently drowning when the breathing gas supply runs out. The equipment aspect largely involves the provision of an adequate breathing gas supply to cover reasonably foreseeable contingencies, redundant dive lights and other safety critical equipment, and the use of a continuous guideline leading the divers back out of the overhead environment. The skills and procedures include effective management of the equipment, and procedures to recover from foreseeable contingencies and emergencies, both by individual divers, and by the teams that dive together.

Despite these risks, water-filled caves attract scuba divers, cavers, and speleologists due to their often unexplored nature, and present divers with a technical diving challenge. Underwater caves have a wide range of physical features, and can contain fauna not found elsewhere. Several organisations dedicated to cave diving safety and exploration exist, and several agencies provide specialised training in the skills and procedures considered necessary for acceptable safety.

Cavern diving

Cavern diving is an arbitrarily defined, limited scope activity of diving in the naturally illuminated part of underwater caves, where the risk of getting lost is small, as the exit can be seen, and the equipment needed is reduced due to the limited distance to surface air. It is defined as a recreational diving activity as opposed to a technical diving activity on the grounds of low risk and basic equipment requirements.^[5]^[6]

Ice diving

Ice diving is a type of penetration diving where the dive takes place under ice.^[7]^[8] Because diving under ice places the diver in an overhead environment typically with only a single entry/exit point, it requires special procedures and equipment. Ice diving is done for purposes of recreation, scientific research, public safety (usually search and rescue/recovery) and other professional or commercial reasons.^[9]

The most obvious hazards of ice diving are getting lost under the ice, hypothermia, and regulator failure due to freezing. Scuba divers are generally tethered for safety. This means that the diver wears a harness to which a line is secured, and the other end of the line is secured above the surface and monitored by an attendant. Surface supplied equipment inherently provides a tether, and reduces the risks of regulator first stage freezing as the first stage can be managed by the surface team, and the breathing gas supply is less limited. For the surface support team, the hazards include freezing temperatures and falling through thin ice.

Wreck penetration diving

Penetration diving in shipwrecks is done as a recreational activity and as a professional activity in salvage and clearance work.

Wreck diving

Wreck diving is recreational diving where the wreckage of ships, aircraft and other artificial structures are explored. The term is used mainly by recreational and technical divers. Professional divers, when diving on a shipwreck, generally refer to the specific task, such as salvage work, accident investigation or archaeological survey. Although most wreck dive sites are at shipwrecks, there is an increasing trend to scuttle retired ships to create artificial reef sites. Diving to crashed aircraft can also be considered wreck diving.^[10] The recreation of wreck diving makes no distinction as to how the vessel ended up on the bottom.

Some wreck diving involves penetration of the wreckage, making a direct ascent to the surface impossible for a part of the dive.

Salvage diving

Salvage diving is the diving work associated with the recovery of all or part of ships, their cargoes, aircraft, and other vehicles and structures which have sunk or fallen into water. In the case of ships it may also refer to repair work done to make an abandoned or distressed but still floating vessel more suitable for towing or propulsion under its own power.^[11]^[12]^[13] The recreational/technical activity known as wreck diving is generally not considered salvage work, though some recovery of artifacts may be done by recreational divers.

Most salvage diving is commercial work, or military work, depending on the diving contractor and the purpose for the salvage operation, Similar underwater work may be done by divers as part of forensic investigations into accidents, in which case the procedures may be more closely allied with underwater archaeology than the more basic procedures of advantageous cost/benefit expected in commercial and military operations.

Savage work that may require penetration of flooded internal spaces or diving under the vessel includes surveys of underwater damage, patching, shoring and other reinforcement, and attachment of lifting gear.^[11]

Clearance diving

Clearance diving, the removal of obstructions and hazards to navigation, is closely related to salvage diving, but has a different purpose, in that the objects to be removed are not intended to be recovered, just removed or reduced to a condition where they no longer constitute a hazard or obstruction. Many of the techniques and procedures used in clearance diving are also used in salvage work.^[12]

Diving under ships

The underside of the hull is an overhead environment with no direct vertical access to the surface. As such it constitutes an entrapment hazard, particularly under large vessels where it may be too dark due to low natural light or turbid water to see the way to the side of the hull. The bottom of the largest ships is mostly flat and featureless, exacerbating the problem, and as the plating is almost always steel, a magnetic compass is not reliable for navigation. Only surface-supplied diving is authorised for this work in most jurisdictions, as this not only secures the diver's breathing gas supply, but also provides a guideline to the exit point. There is also a hazard of crushing if the clearance is small and the tide range is large.

Sewer diving

Safety and risk management

The main generic hazards of penetration diving are being unable to navigate back to the surface and running out of breathing gas before reaching the surface. Both of these hazards are well mitigated by the use of surface supplied breathing equipment, but at the cost of seriously reduced mobility and extremely restricted range, to the extent that some penetration activities are impossible on surface supply.

Scuba diving

For scuba diving, the risk of getting lost and running out of breathing gas is real and significant. These are the most common factors recorded in diving deaths in penetration diving. The use of a continuous guideline leading to open water is recognised as the most important safety precaution in any overhead environment with a real possibility of not being able to see the way out, along with sufficient emergency gas to compensate for any single catastrophic breathing gas supply failure at any time during the planned course of a penetration dive.

Surface supplied diving

Surface supplied diving reduces the risk of getting lost under an overhead, as the umbilical provides a reliable guideline back to the entry point, and a reliable source of breathing gas with a low risk of out of air incidents, but it can be cumbersome, only allows a limited penetration distance based on available umbilical length and the ability of the diver to drag it along and the ability of the tenders to drag it back during exit, and can become snagged on obstructions or diverted through line traps. It may need one or more in-water tenders or guide hoops to avoid these problems, and it may not be possible for the standby diver to reach the diver within an acceptable time in an emergency. Another possible problem is hydrodynamic drag in a current.

Equipment

All critical life-support equipment must be sufficiently redundant to allow escape in any reasonably foreseeable failure scenario.

Skills, procedures, and training

Skills and procedures have been developed for managing the hazards and foreseeable contingencies associated with different circumstances of penetration diving and the equipment suitable for use in each environment. These are generally learned in training for diving in those specific environments, but most are applicable across a range of environments with similar hazards.

Related Research Articles

Ice diving is a type of penetration diving where the dive takes place under ice. Because diving under ice places the diver in an overhead environment typically with only a single entry/exit point, it requires special procedures and equipment. Ice diving is done for purposes of recreation, scientific research, public safety and other professional or commercial reasons.

Technical diving is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to a greater risk of serious injury or death. Risk may be reduced via appropriate skills, knowledge, and experience. Risk can also be managed by using suitable equipment and procedures. The skills may be developed through specialized training and experience. The equipment involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources.

Wreck diving is recreational diving where the wreckage of ships, aircraft and other artificial structures are explored. The term is used mainly by recreational and technical divers. Professional divers, when diving on a shipwreck, generally refer to the specific task, such as salvage work, accident investigation or archaeological survey. Although most wreck dive sites are at shipwrecks, there is an increasing trend to scuttle retired ships to create artificial reef sites. Diving to crashed aircraft can also be considered wreck diving. The recreation of wreck diving makes no distinction as to how the vessel ended up on the bottom.

Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other cave users. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave-diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave-diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave-diving and cavern-diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water surface may also be specified.

Diving activities are the things people do while diving underwater. People may dive for various reasons, both personal and professional. While a newly qualified recreational diver may dive purely for the experience of diving, most divers have some additional reason for being underwater. Recreational diving is purely for enjoyment and has several specialisations and technical disciplines to provide more scope for varied activities for which specialist training can be offered, such as cave diving, wreck diving, ice diving and deep diving. Several underwater sports are available for exercise and competition.

Recreational diving or sport diving is diving for the purpose of leisure and enjoyment, usually when using scuba equipment. The term "recreational diving" may also be used in contradistinction to "technical diving", a more demanding aspect of recreational diving which requires more training and experience to develop the competence to reliably manage more complex equipment in the more hazardous conditions associated with the disciplines. Breath-hold diving for recreation also fits into the broader scope of the term, but this article covers the commonly used meaning of scuba diving for recreational purposes, where the diver is not constrained from making a direct near-vertical ascent to the surface at any point during the dive, and risk is considered low.

<span class="mw-page-title-main">Scuba diving</span> Swimming underwater, breathing gas carried by the diver

Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The name scuba is an anacronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.

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.

In scuba diving, the rule of thirds is a rule of thumb used by divers to plan dives so they have enough breathing gas remaining in their diving cylinder at the end of the dive to be able to complete the dive safely. This rule generally only applies to diving in overhead environments, such as caves and wrecks, where a direct ascent to the surface is impossible and the divers must return the way they came.

A silt out or silt-out is a situation when underwater visibility is rapidly reduced to functional zero by disturbing fine particulate deposits on the bottom or other solid surfaces. This can happen in scuba and surface supplied diving, or in ROV and submersible operations, and is a more serious hazard for scuba diving in penetration situations where the route to the surface may be obscured.

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 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.

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.

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

The following index is provided as an overview of and topical guide to underwater diving: Links to articles and redirects to sections of articles which provide information on each topic are listed with a short description of the topic. When there is more than one article with information on a topic, the most relevant is usually listed, and it may be cross-linked to further information from the linked page or section.

Scuba diving tourism is the industry based on servicing the requirements of recreational divers at destinations other than where they live. It includes aspects of training, equipment sales, rental and service, guided experiences and environmental tourism.

Recreational scuba certification levels are the levels of skill represented by recreational scuba certification. Each certification level is associated with a specific training standard published by the certification agency, and a training programme associated with the standard., though in some cases recognition of prior learning can apply. These levels of skill can be categorised in several ways:

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.

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

References

↑ Code of Practice for Scientific Diving (PDF). Pretoria: The South African Department of Labour. Archived from the original (PDF) on 9 November 2016. Retrieved 9 November 2016.
↑ Barsky, Steven (2007). Diving in High-Risk Environments (4th ed.). Ventura, California: Hammerhead Press. ISBN 978-0-9674305-7-7.
↑ Jablonski, Jarrod (2006). "9: Diving environments". Doing It Right: The Fundamentals of Better Diving. High Springs, Florida: Global Underwater Explorers. p. 137. ISBN 978-0-9713267-0-5.
↑ "Cave diving restrictions". deepdarkdiving.com. Retrieved 19 September 2023.
1 2 "How cavern and cave diving differ". cavediving.com. Retrieved 17 June 2022.
↑ "How does cavern and cave diving differ from one another". 19 August 2009. Retrieved 17 June 2022.
↑ Lang, M.A.; Stewart, J.R., eds. (1992). AAUS Polar Diving Workshop Proceedings (PDF). United States: Scripps Institution of Oceanography, La Jolla, CA. p. 100.
↑ Lang, Michael A.; Sayer, M.D.J., eds. (2007). Consensus recommendations (PDF). Proceedings of the International Polar Diving Workshop, Svalbard. Washington, DC.: Smithsonian Institution. pp. 211–213.
↑ Smith, R. Todd; Dituri, Joseph (August 2008). "26: Expeditions ~ Arctic Ice Diving". In Mount, Tom; Dituri, Joseph (eds.). Exploration and Mixed Gas Diving Encyclopedia (1st ed.). Miami Shores, Florida: International Association of Nitrox Divers. pp. 297–304. ISBN 978-0-915539-10-9.
↑ "The Search is in the Planning". Canadian Harvard Aircraft Association Dive Recovery Team. 2008. Archived from the original on 13 June 2015.
1 2 U.S. Navy Salvage Manual (PDF). Vol. 1: Strandings, Harbor Clearance and Afloat Salvage S0300-A6-MAN-010. United States. Navy Department. Supervisor of Salvage and Diving. 31 May 2013. This article incorporates text from this source, which is in the public domain.
1 2 US Navy (2006). US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. Retrieved 2008-06-15.
↑ U.S. Navy Salvage Manual (PDF). Vol. 4: Deep Ocean Operations S0300-A6-MAN-040 0910-LP-252-3200. United States. Navy Department. Supervisor of Salvage and Diving. 1 August 1993. This article incorporates text from this source, which is in the public domain.

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[CoP_Scientific-1] Code of Practice for Scientific Diving (PDF). Pretoria: The South African Department of Labour. Archived from the original (PDF) on 9 November 2016. Retrieved 9 November 2016.

[High_risk-2] Barsky, Steven (2007). Diving in High-Risk Environments (4th ed.). Ventura, California: Hammerhead Press. ISBN 978-0-9674305-7-7.

[Jablonski_2006-3] Jablonski, Jarrod (2006). "9: Diving environments". Doing It Right: The Fundamentals of Better Diving. High Springs, Florida: Global Underwater Explorers. p. 137. ISBN 978-0-9713267-0-5.

[restrictions-4] "Cave diving restrictions". deepdarkdiving.com. Retrieved 19 September 2023.

[cavedivingdotcom-5] 1 2 "How cavern and cave diving differ". cavediving.com. Retrieved 17 June 2022.

[scuba.com-6] "How does cavern and cave diving differ from one another". 19 August 2009. Retrieved 17 June 2022.

[aaus1992-7] Lang, M.A.; Stewart, J.R., eds. (1992). AAUS Polar Diving Workshop Proceedings (PDF). United States: Scripps Institution of Oceanography, La Jolla, CA. p. 100.

[smithsonian2007-8] Lang, Michael A.; Sayer, M.D.J., eds. (2007). Consensus recommendations (PDF). Proceedings of the International Polar Diving Workshop, Svalbard. Washington, DC.: Smithsonian Institution. pp. 211–213.

[Smith_and_Dituri_2008-9] Smith, R. Todd; Dituri, Joseph (August 2008). "26: Expeditions ~ Arctic Ice Diving". In Mount, Tom; Dituri, Joseph (eds.). Exploration and Mixed Gas Diving Encyclopedia (1st ed.). Miami Shores, Florida: International Association of Nitrox Divers. pp. 297–304. ISBN 978-0-915539-10-9.

[CHAA-10] "The Search is in the Planning". Canadian Harvard Aircraft Association Dive Recovery Team. 2008. Archived from the original on 13 June 2015.

[Salvage_manual_010-11] 1 2 U.S. Navy Salvage Manual (PDF). Vol. 1: Strandings, Harbor Clearance and Afloat Salvage S0300-A6-MAN-010. United States. Navy Department. Supervisor of Salvage and Diving. 31 May 2013. This article incorporates text from this source, which is in the public domain.

[USN_Diving_Manual_R6-12] 1 2 US Navy (2006). US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. Retrieved 2008-06-15.

[Salvage_manual_040-13] U.S. Navy Salvage Manual (PDF). Vol. 4: Deep Ocean Operations S0300-A6-MAN-040 0910-LP-252-3200. United States. Navy Department. Supervisor of Salvage and Diving. 1 August 1993. This article incorporates text from this source, which is in the public domain.

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