deep-sea Diving

Diving, deep-sea, descent by divers to the seabed, usually for extended periods, for purposes of exploration, recreation, or salvage. In 1715 John Lethbridge devised the forerunner of the armored suits used today in deepest waters. In 1802 William Forder devised a suit into which air is supplied by a pump. The diving suit today has a metal or fiberglass helmet with viewports and inhalation and exhalation valves, joined by an airtight seal to a metal chestpiece, itself joined to a flexible watertight covering of rubber and canvas; weights, especially weighted boots, provide stability and prevent the diver from shooting toward the surface. Air or, more often, an oxygen/helium mixture is conveyed to the diver via a thick rubber tube. Nowadays, self-contained underwater breathing apparatus (scuba diving), where the diver has no suit but carries gas cylinders and an aqualung, permits great mobility. In all diving great care must be taken for proper decompression to avoid the bends, a dangerous condition in which gas bubbles enter the blood and tissue during overly rapid ascent to the surface.