The hatch would not open.
Six hundred feet below the surface of the Pacific Ocean off the Southern California coast, Chief Warrant Officer Bob Barth struggled to get inside the Navy’s new Sealab 3 habitat. The 340-ton undersea platform, where he and a nine-man crew were scheduled to spend 12 days together, was leaking. Mr. Barth and a fellow diver, Berry L. Cannon, had headed down with two other divers to fix it.
Suddenly, Mr. Barth realized that Mr. Cannon was suffering convulsions, his respirator floating free and his jaws clenched shut so that it could not be reinserted.
The scene played out on the closed-circuit television monitoring the habitat from the surface; Mr. Barth frantically tried to get his crewmate back to the diving pod where the other two divers waited. One of them, Richard Blackburn, helped wrestle Mr. Cannon back into the capsule for the slow return to the surface. As they rose, they attempted to resuscitate Mr. Cannon, but without luck; using their intercom, they called to the surface to say he had died.
Mr. Cannon’s death marked the end of one of the great programs of naval exploration, one that began with a dry-land test called Genesis and moved through three versions of the Sealab underwater habitat, from the late 1950s to 1969. The program greatly increased the depths at which humans could safely live and work. The divers were called aquanauts, an under-the-sea analogue to the glamorous astronauts who circled the earth and landed on the moon.
Only one aquanaut was deeply involved in all four stages of that grand adventure: Mr. Barth, who died on March 26 at his home in Panama City, Fla., at 89. The cause was complications of Parkinson’s disease, said his son, Dale.
The dangerous experiments Mr. Barth took part in paved the way for exploits of deepwater espionage, undersea construction and demolition projects around the world.
He never achieved conventional fame, but he was the “ultimate aquanaut,” said Leslie Leaney, the executive director of the International Scuba Diving Hall of Fame. “His contributions benefited the world of science and national security, but also the economies of all nations that explored for offshore oil.”
In 2010, the Navy named its aquatic training facility in Panama City for Mr. Barth. “Nothing that Navy divers do is one guy,” he said at the dedication. “There is always a whole bunch of people involved in it.”
“Much like the first NASA astronauts of the U.S. space program, Bob Barth volunteered to put himself on the line to do something extraordinary that had never been done,” Mr. Hellwarth said, “and not everyone in the Navy thought it was such a good idea.”
Mr. Barth would say: “Some people called us guinea pigs. They called us a lot of other things, too,” a suggestion that skeptics thought anyone involved in the program was stupid, crazy or both. Many Navy higher-ups doubted that the program could lead to anything useful, Mr. Hellwarth said.
The Sealab program got its start with Capt. George F. Bond, then head of the Medical Research Laboratory at the Naval Submarine Base in Groton, Conn. Mr. Barth was stationed there.
The concept that Captain Bond developed was “saturation diving,” which involves putting divers under high atmospheric pressure before descent and bringing them back to normal very gradually.
Under the pressures of diving, atmospheric gases get forced into the bloodstream and bodily tissues. Come up too fast and the gases bubble out, like the fizz of a carbonated soda when you pop the lid. Without careful decompression, escaping gas can cause the potentially fatal condition known as the bends.
The best mixture of gases for such excursions had to be determined. Under high pressure, too much oxygen becomes toxic. Too much nitrogen can have a narcotic effect. The experiments led to gas mixtures that, for great depths, were composed largely of helium, which made the divers’ voices high-pitched and squeaky.
Helium also transfers heat more quickly than do nitrogen and oxygen, which meant that deep-sea work could expose the pioneering divers to bone-chilling cold. Levels of carbon dioxide had to be carefully managed; Mr. Cannon was poisoned by too much carbon dioxide, and it was later discovered that a canister that was supposed to be filled with a chemical that absorbed the CO2 in recirculated air was empty.
Mr. Barth possessed a natural authority, his former teammate Mr. Blackburn recalled. “He would lead from the front,” he said, meaning that he would be the first to take any risk that was expected of his crew.
Mr. Barth could be profane and direct: “you didn’t want to get on the wrong side of him on a bad day,” Mr. Blackburn said, but added that “he always had some kind of prank up his sleeve.” Friends referred to him as “Sweet Old Bob,” with the abbreviation intentional.
Robert August Barth Jr. was born in Manila, on Aug. 28, 1930, to Robert Sr. and the former Phyllis Ludwig. His father was an Army officer on the staff of Gen. Douglas MacArthur; his mother managed a shoe store. They divorced when he was 10.
According to biographical information provided by Mr. Hellwarth, with the coming of the World War II, Mr. Barth’s mother and her second husband stayed behind while young Bob was put on a ship to the United States, where he rejoined his father. He was later reunited with his mother and stepfather, and they moved to Chicago, and later South Africa.
At 17, Mr. Barth took a job as a seaman on a cargo ship bound for Baltimore; once in the United States he signed on with the Navy, where he encountered Captain Bond.
In 1951, he married the former Georgia Murrow; they had a son, Bobby Barth, a rock musician. They divorced in 1954. In 1958 he married his second wife, the former Joyce Ann Williams, and adopted Dale, her son by her first marriage; the couple had a second child, Samuel, and later divorced. In 2014 he married the former Sharon Kay Kinsey. She survives him, as do his sons.
After retiring from the Navy, he worked in commercial diving, and later took a Civil Service position with the Navy Experimental Diving Unit. In 2000 he published a memoir, “Sea Dwellers.”
The Sealab program included one real-life astronaut, Scott Carpenter, one of the original seven Mercury astronauts and the second man to orbit the earth. Mr. Carpenter died in 2013. His daughter, Kris Stoever, said that he and Mr. Barth “formed a fast friendship.” Mr. Carpenter wrote the foreword to “Sea Dwellers.”
Ms. Stoever’s brothers got a taste of the kinds of pranks that Mr. Barth could pull. One summer two of Mr. Carpenter’s children, Matthew and Nick, came to the family vacation home at Palmer Lake in Colorado while Mr. Barth was visiting. They were preteens, and their father was trying without success to interest the boys in the maritime art of tying knots. “The boys didn’t want to do it,” Ms. Stoever said. “Bob Barth tied them to a tree.”
Matthew, in retrospect, finds it funny, Ms. Stoever said; Nick does not.
Neither could recall the knots Mr. Barth employed.