The Interdependence between Ocean Depth and Pressure in Scuba Diving


Related Posts:

This picture shows colorful underwater corals and anemones in hues of yellow, orange, green, and brown, surrounded by water that appears blue in color.
Scuba divers, whether at the Great Barrier Reef or in the Caribbean, must be aware of buoyancy, pressure equalization, and the amount of time they spend underwater, to avoid the risks associated with pressurized gases in the body. (credit: Kyle Taylor)

The Interdependence between Ocean Depth and Pressure in Scuba Diving (OpenStax Chemistry 2e)

Whether scuba diving at the Great Barrier Reef in Australia or in the Caribbean, divers must understand how pressure affects a number of issues related to their comfort and safety.

Pressure increases with ocean depth, and the pressure changes most rapidly as divers reach the surface. The pressure a diver experiences is the sum of all pressures above the diver (from the water and the air). Most pressure measurements are given in units of atmospheres, expressed as “atmospheres absolute” or ATA in the diving community: Every 33 feet of salt water represents 1 ATA of pressure in addition to 1 ATA of pressure from the atmosphere at sea level. As a diver descends, the increase in pressure causes the body’s air pockets in the ears and lungs to compress; on the ascent, the decrease in pressure causes these air pockets to expand, potentially rupturing eardrums or bursting the lungs. Divers must therefore undergo equalization by adding air to body airspaces on the descent by breathing normally and adding air to the mask by breathing out of the nose or adding air to the ears and sinuses by equalization techniques; the corollary is also true on ascent, divers must release air from the body to maintain equalization. Buoyancy, or the ability to control whether a diver sinks or floats, is controlled by the buoyancy compensator (BCD). If a diver is ascending, the air in his BCD expands because of lower pressure according to Boyle’s law (decreasing the pressure of gases increases the volume). The expanding air increases the buoyancy of the diver, and she or he begins to ascend. The diver must vent air from the BCD or risk an uncontrolled ascent that could rupture the lungs. In descending, the increased pressure causes the air in the BCD to compress and the diver sinks much more quickly; the diver must add air to the BCD or risk an uncontrolled descent, facing much higher pressures near the ocean floor. The pressure also impacts how long a diver can stay underwater before ascending. The deeper a diver dives, the more compressed the air that is breathed because of increased pressure: If a diver dives 33 feet, the pressure is 2 ATA and the air would be compressed to one-half of its original volume. The diver uses up available air twice as fast as at the surface.


Flowers, P., Theopold, K., Langley, R., & Robinson, W. R. (2019, February 14). Chemistry 2e. Houston, Texas: OpenStax. Access for free at:


Related Research

Research Article: The influence of scuba diving experience on divers’ perceptions, and its implications for managing diving destinations

Date Published: July 5, 2019 Publisher: Public Library of Science Author(s): Serena Lucrezi, Martina Milanese, Carlo Cerrano, Marco Palma, Agnese Marchini. Abstract: Scuba diving experience–which can include accumulated diving experience and familiarity with a diving location–is an important descriptor of diver specialisation and behaviour. Formulating and applying generalisations on scuba diving experience and its … Continue reading

Research Article: Stirring the strategic direction of scuba diving marine Citizen Science: A survey of active and potential participants

Date Published: August 16, 2018 Publisher: Public Library of Science Author(s): Serena Lucrezi, Martina Milanese, Marco Palma, Carlo Cerrano, Carlo Nike Bianchi. Abstract: Citizen Science (CS) strengthens the relationship between society and science through education and engagement, with win-win benefits. Marine Citizen Science (MCS) is increasingly popular, thanks to society’s growing interest in marine … Continue reading

Research Article: Mobility, Expansion and Management of a Multi-Species Scuba Diving Fishery in East Africa

Date Published: April 17, 2012 Publisher: Public Library of Science Author(s): Hampus Eriksson, Maricela de la Torre-Castro, Per Olsson, Sebastian C. A. Ferse. Abstract: Scuba diving fishing, predominantly targeting sea cucumbers, has been documented to occur in an uncontrolled manner in the Western Indian Ocean and in other tropical regions. Although this type of fishing … Continue reading

Research Article: Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial

Date Published: May 10, 2016 Publisher: Public Library of Science Author(s): Vincent Souday, Nick J. Koning, Bruno Perez, Fabien Grelon, Alain Mercat, Christa Boer, Valérie Seegers, Peter Radermacher, Pierre Asfar, Thomas Penzel. Abstract: To test the hypothesis whether enriched air nitrox (EAN) breathing during simulated diving reduces decompression stress when compared to compressed air … Continue reading