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In the pressurized, artificial atmosphere of the capsule, life can be trying and topsy-turvy. Matches will not burn and water boils only at temperatures above 300°. Fried foods are forbidden because of the greasy fumes. Fresh eggs can be dangerous: the toxic hydrogen sulfide given off by their yokes cannot be "scrubbed" out of the air with Sealab's purifying gear. The atmosphere has to be rigidly controlled. Because ordinary concentrations of oxygen become toxic when breathed under pressure for a long period (causing convulsions and pulmonary disease) and nitrogen has a narcotic effect, the aquanauts breathe a special mixture of gases: 4.3% oxygen, 18% nitrogen, and the rest helium. Even this mix is not perfect. Helium is so much lighter and less dense than nitrogen that the human voice resounds at a higher pitch than normal and words tumble out rapidly, producing a Donald Duck falsetto. To make themselves understood, the men must speak an octave lower and much slower than usual.
Deep Dangers. The aquanauts are doing more work than had been expected. They have set up an outdoor station to measure ocean currents, and are performing about 100 marine biology and oceanography experiments. Each morning at least two of them put on rubber "wet" suits, strap on Mark VI breathing apparatus and slip out through a hatch on the bottom of the capsule. (The hatches can be held open without flooding the Sealab because the pressure inside is equal to the pressure of the water outside.)
The sea's extreme cold limits trips in ordinary wet suits to two hours at most, and darkness and the dangers of the deep prevent the aquanauts from venturing beyond a 225-ft. perimeter. Neither do they swim more than 30 ft. up or down, lest they fall victim to the deep-sea diver's greatest fear—the bends. If a diver comes up too fast, gases that have dissolved in his bloodstream from breathing under pressure form bubbles that lead to dizziness, nausea or even death.
On the sorties outside, the aquanauts photograph the neighborhood, tag fish to record their movements, and collect marine samples. They are building concrete-block pyramids as fish homes, and will lay "sidewalks" with a gelatin mixture that is expected to harden into firm surface on the soft ocean floor. To experiment with underwater salvage, the Navy will sink an old fighter plane, have the aquanauts fill it with lightweight polyurethane foam, then see if the foam displaces enough water and is buoyant enough for the plane to float to the surface.
The aquanauts this week expect to get some help from a 7-ft., 270-lb. bottlenose porpoise named Tuffy. Trained by the Navy, Tuffy has been taught to come swimming at the sound of a buzzer. He will live in a pen near the support barge, carry messages and cables between the lab, its divers, and topside.
Blooming Health. As the first team prepared to leave the lab and be replaced by a second crew last week, the men were physically in top shape, except for minor ear infections that are common to divers who use hooded swim suits. Doctors reported that the men were in excellent psychological health. Sealab's Captain Bond was particularly impressed with the aquanauts' performance. "That's what this experiment is all about," he says, "to see what man can do underwater."