Scuba Diving Physics







Page created by Heather C. Hopkins

Last updated 11/25/2009

Scuba Diving Dangers:

Scuba diving is an experience of a lifetime.  There are quite a few hazards related to scuba diving, but these can usually be avoided with basic understanding of physics.  Many safety tips are created on the basis of physics concepts, and being conscientious of them can help prevent divers from harm.  Some dangers to watch out for include:

Photo of coral and clown fish, courtesy of NOAA at

Because of pressure, divers must be especially careful when they come up to the surface.  One of the most important things a diver should know is to breathe normally, especially during ascent.  Since the volume of gas expands with decreasing pressure, if a diver holds their breath while ascending, they can potentially harm themselves.  These unequal air pressures (barotrauma) can cause extensive damage.  Compression or decompression can destroy tissues, cause swelling, and block blood supply.

DCS (Decompression Sickness):

During a dive, nitrogen gas is compressed due to increased pressure underwater.  The compressed form then dissolves faster into a diver's bloodstream. In addition, the deeper the dive, the more nitrogen absorbed by a diver's body.  A diver coming to the surface must be careful, because as the pressure decreases (decompression), "off-gassing" happens.  This is when excess nitrogen dissolves out of the diver's body, which results in small nitrogen bubbles exhaled through the lungs.  When there is too much nitrogen released too fast, the nitrogen can damage tissues in the diver's body.  These may result in symptoms of decompression sickness (DCS), which may potentially be fatal.

Divers must also be careful about flying after diving.  Even though an airplane cabin is pressurized, they are only pressurized to approximately 8,000 feet.  This is still a significant 25% pressure decrease from sea level.  During an airplane's ascent to a lesser atmosphere of pressure (decompression), "off-gassing" can happen.  This can be dangerous at lower pressures, and may cause symptoms of DCS.  Therefore, divers must take care to allow enough time for all the nitrogen to be released from their bloodstream before flying on an airplane.  Many researchers suggest a 24 hour period between diving and flying.

No Decompression Table, Avoid DCS
A dive table used to prevent divers from getting decompression sickness, courtesy of Medscape at