With a flutter of powerful fin kicks Ravelo propels himself downward. At fifty feet the increasing water pressure compresses the air-filled cavities in his body to a density sufficient for him to sink without effort. He stops kicking, and the force of gravity slices him through the water like an arrow surging toward its target. They have a deep love of the sea. You cannot understand the strength of their passion.
Gamba points out that human beings have long braved the sea unaided by gadgets.
Archaeological digs have unearthed widespread evidence of breath-hold diving in seaside cultures. Mother of pearl, for example, harvested from the deep, adorns carved ornaments that date from 3200 B.C. in Thebes and 4500 B.C. in Mesopotamia. Today in Japan female divers known as amas scavenge the ocean floor for pearls and coral at depths of as much as 145 feet for up to three hours a day, returning to the surface as many as ninety times for air. Scuba divers at those depths for this duration would suffer decompression sickness. The ama practice of whistling before a plunge seemed only a custom until scientists discovered that whistling increases air pressure in the lungs, forcing blood out and leaving more volume for the next breath.