Walter Mazzone; Directed Navy Underwater Feats

Capt. Walter F. Mazzone played a pivotal role in two underwater Navy exploits during the 20th century. In World War II, he kept a waterlogged submarine from going belly up while it was carrying 40 Americans rescued from the Philippines. Twenty years later he helped organize the first Sealab tests of human endurance at crushing ocean depths — conducting the first tests on himself — which established the deepwater diving protocols still used by military and commercial divers today.

Captain Mazzone, who died on Aug. 7 at 96 in San Diego, was considered one of the Navy’s most exacting detail men in the underwater realm — where a millimeter’s leak, a workaday tangle and a molecule-size mistake are life-or-death matters.

On submarines, Captain Mazzone (pronounced mah-ZOH-nee) was the diving officer, in charge of taking the sub down, surfacing it and keeping it on an even keel when under attack. On Sealab experiments, he was the life-support man — helping divers descend hundreds of feet, stay below for weeks at a time and come back alive through a method he helped develop called “saturation diving.”

Capt. Walter F. Mazzone in the foreground with Capt. George F. Bond as they prepared to visit Sealab II off California in 1965. Credit U.S. Navy

Captain Mazzone, who was awarded the Silver Star and other medals, left the Navy after the war but rejoined it in the late 1950s to work with Capt. George F. Bond and others on research that would become the backbone of the Navy’s Sealab project.

In 1962, the team launched the 57-foot-long sausage-shaped underwater chamber known as Sealab I, which upended the conventional wisdom that, even with oxygen tanks, divers could not survive at a depth of more than 150 feet for more than a half-hour. The four divers in Sealab I remained at a depth of 192 feet for 11 days.

Captain Bond, a medical doctor, had pioneered the technique that made it possible: saturation diving, which virtually rewrote the chemistry of human respiration and temporarily transformed human divers into marine mammals.

The method involved replacing the sea-level mix of air (about 80 percent nitrogen and 20 percent oxygen) with a different mix (90 percent helium and 10 percent or less of oxygen) that could sustain human life underwater at great depths.