- Scuba Diving
- See Scuba diving emergencies
- Underwater diving with the use of a compressed air cylinder, a regulator, a buoyancy compensator, and additional gear that generally includes a wetsuit, fins, mask, dive watch, weights.
- Requires certification, generally through PADI or NAUI
- Divers Alert Network, DAN emergency hotline phone number (919) 684-9111
- Free Diving
- Underwater diving without supplemental oxygen, dating back thousands of years to early shellfish divers. Additional gear may include weights, fins, suit, dive watch.
- Competitive extreme sport, with several sub-categories. Deepest "no limits" depth records for males (214m, 702ft), females (160m, 525ft)
- Usually surface or shallow water swimming with the use of a snorkel to allow continuous breathing while the face remains submerged. Often used in resorts or tropical areas.
- Rebreather Diving
- Tethered Diving
- Surface supplied gas supplied by a hose from a source or a diving bell.
- Most often used in commercial or military diving, often in settings with little to no visibility.
- Pascals Law applies to the diving body (without air filled areas such as lungs) states that the pressure applied to any part of the enclosed liquid will be transmitted equally in all directions through the liquid.
- Boyles Law applies to the diving body's air filled areas such as lungs, sinuses, middle ear, and states that the volume and pressure of a gas at a given temperature are inversely related.
- At 2 ATA (10m/33ft) a given gas would be 1/2 it's volume, at 3 ATA (20m/66ft) it would be 1/3 it's volume and so on.
- Barotrauma of descent
- Barotrauma of ascent
- At depth injuries
- Hyperbaric Medicine
- Scuba diving emergencies