Wikipedia
Precontinent is a name of a set of projects to build an underwater "village" carried out by Jacques-Yves Cousteau and his team. The projects were named Precontinent I, Precontinent II and Precontinent III. Each following project was aimed at increasing the depth at which people continuously lived under water.
The aim of these three projects was to show that people could live underwater for prolonged periods of time, while being subjected to the harsh environments of the deep sea. The pressure in the village buildings was regulated to that of the surrounding water, so that people could explore the environment around them. This required adjustments of the air mixture supplied to the buildings.
Precontinent I was constructed offshore from Marseille, France, in 1962. Two scuba divers spent two weeks in a small chamber 12 meters deep on the seabed.
Precontinent II was placed in the Red Sea near Shaab Rumi off the coast of Sudan. Five structures were set up to house eight divers and their equipment. Two support ships on the surface provided compressed air and other logistical support to Precontinent II. When the experiment ended, two structures were dismantled and removed. The rest became undersea destinations for recreational divers.