Underwater diving is the practice of descending below the water's surface to interact with the environment. Humans are not biologically adapted for deep diving, and must use special equipment to extend the depth and duration of their dives. In ambient pressure diving, with direct exposure to the pressure of the surrounding water, the diver can use breathing apparatus for scuba diving or surface-supplied diving. For repeated deep dives, divers can reduce the risk of decompression sickness by living in a pressurized environment on the surface to prevent pressurization and depressurization as they dive. Atmospheric diving suits may be used to isolate the diver from high ambient pressure. Diving activities are restricted to maximum depths of about 40 metres (130 ft) for recreational scuba diving, 530 metres (1,740 ft) for commercial saturation diving, and 610 metres (2,000 ft) if atmospheric suits are worn. The history of breath-hold diving goes back at least to classical times, and there is evidence of prehistoric hunting and gathering of seafoods that may have involved underwater swimming. (Full article...)
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