George Bond, left, the father of Sealab, and Walter Mazzone, his right-hand man, check a pressure chamber with three volunteer test subjects living inside.

Bob Barth prepares for a long stay inside a pressure chamber.

Capt. George Bond and the first aquanauts stand with Sealab I before a trial run in 1964.

Robert Thompson and Tiger Manning inside the first Sealab “habitat,” a prototype shelter for divers living on the seabed.

The first aquanaut team for Sealab II, which included Mercury astronaut Scott Carpenter.

Sealab III arrives at Long Beach, Calif., in 1968, en route to its place on the seabed.