Diving

An open-bottomed bell trapped a pocket of air as it descended. A 1562 salvage treatise shows such a device, while later bells received replacement air in lowered barrels. The bell extended time at depth but kept the diver close to one small refuge.

Compressed-air workers and divers sometimes became ill after returning to lower pressure. Paul Bert connected the illness with dissolved nitrogen, and John Scott Haldane's staged ascent work helped turn pressure exposure into planned decompression. Getting down was only half the problem.

Jacques-Yves Cousteau and Émile Gagnan adapted a demand regulator to deliver compressed air at the surrounding pressure. Their Aqua-Lung was an important practical system in a longer sequence of self-contained apparatus. It freed the diver from a surface hose and made three-dimensional movement routine.

Underwater habitats asked whether people could remain at pressure for days rather than visit for minutes. Edwin Link, Jacques Cousteau and other teams tested chambers, houses and saturation routines. The projects expanded scientific access while showing how much support life at depth requires.

Recreational divers now enter reefs, kelp forests, lakes, quarries and wrecks using training inherited from working and scientific practice. A modern dive is a negotiated limit: weather, visibility, current, depth, gas, access and the condition of the place itself.