Bill Stone will never forget the day he began to make diving history by immersing himself in Wakulla Springs, a network of submerged caves in northern Florida. On the early afternoon of December 3, 1987, he swam to a depth of about 30 feet and settled in, carrying only two 30-cubic-foot oxygen tanks and a sack of "blood and gore" war novels. Had he been using normal scuba gear, he would have had to surface after 30 minutes. But Stone, an automation engineer at the National Institute of Standards and Technology in Washington, D.C., was wearing a homemade rebreather. He didn't come up for 24 hours - the longest anyone has ever survived underwater with a self-contained breathing device. "When I got out of the water and checked, I found I'd used only half of my consumables. That was the big shock. I could have stayed under for another 24 hours," he says.
Stone's rebreather recycles his exhaled air, scrubbing it of poisonous carbon dioxide and squeezing out every last molecule of oxygen in his tanks. His inventiveness has transformed the ability of humans to carry out scientific exploration underwater. With rebreathers, divers can linger for half a day without thinking about their air supply, exploring previously undivable undersea caves, surveying shipwrecks, or just passing time with the fish.
