How far underwater can humans swim without being crushed?

Answer 1

Water won't crush you at any depth if you are able to fill your body cavities (lungs, middle ear, sinuses) with compressed air at the same pressure as the water. If you don't have compressed air to breathe you will have a very difficult time going more than 500 feet down without suffocating, not from the pressure, but from the time it takes to travel that far while holding your breath. In any event, your body will not have been crushed because it is mostly incompressible water.

If you don't clear your ears (equalize pressure in the middle ear) you can rupture an eardrum in the deep end of a swimming pool.

Answer 2

Recreational divers are certified by the recreational training agencies (PADI, NAUI, SSI, BSAC, etc) to depths as deep as 130 feet. Most recreational diving takes place above 100 feet and many regional dive operator organizations, including the Cayman Islands Watersports Association, officially limit dives to 100 feet. In fact, most recreational dives occur in relatively shallow depths of 60 feet or less, since most coral and sea life exists above those depths. Scuba diving, however, is not limited to recreational diving. Self Contained Underwater Breathing Apparatus (SCUBA) allows technical and commercial diving to depths well in excess of 130 feet. Humans reach a physiological limit of about 210 feet using normal air as a breathing gas. Below this depth, the oxygen in air reaches partial pressures that become toxic. For this reason, deeper dives are accomplished using mixed breathing gases that contain reduced perentages of oxygen. Deeper depths also increase the risk of decompression illness (also called the "bends"), caused by intert gases (primarily nitrogen) being absorbed by body tissues during prolonged exposure at elevated pressures. Ascending divers require "decompression stops" during ascent to allow time for these absorbed gases to escape from body tissues. It is to avoid these mandatory decompression stops that recreational divers are limited to 130 feet. With the right training, equipment and breathing gas, scuba dives have been made to great depths. The current record for an open circuit scuba dive is 318M (1042 feet). This dive required over 8 hours of decompression stops during the ascent.

Answer 3

Because a person is mostly made up of liquid - which does not compress, and the air spaces such as the lungs are equalized with the surrounding pressure by breathing from the scuba cylinder.

Answer 4

Maximum depth for a recreational scuba diver is 130 feet.