Hannes Keller, Swiss Deep-Sea Diving Pioneer, Is Dead at 88

Hannes Keller, a Swiss mathematician and inspired amateur explorer, planned his audacious deep ocean dive for more than a year. In December 1962, he intended to descend deeper than anyone before him: 1,000 feet down, off Santa Catalina Island, near Los Angeles, in a diving bell called the Atlantis.

“If a man could go, for instance, to 1,000 feet down and do practical work,” Mr. Keller wrote in The Sydney Morning Herald, “then all the continental shelf zone could be explored, a total of more than 16 million square miles.”

Mr. Keller and his expedition partner, Peter Small, a journalist and a veteran diver, knew that critical to the mission would be how well the gas they breathed mitigated the possibility of getting “the bends” — the potentially deadly decompression sickness caused when bubbles of nitrogen form in divers’ bodies during rapid ascents.

Mr. Keller enlisted the help of a cardiopulmonary specialist in Zurich and an IBM computer to conceive a secret formula of oxygen, nitrogen and helium, as well as a plan to dispense it at different mixtures at different depths.

The descent, on Dec. 3, 1962, went well — “Anybody can go down,” Mr. Keller told Life magazine in 1961 — but when Mr. Keller exited the Atlantis on the floor of the Pacific Ocean to plant Swiss and American flags, his breathing hoses became entangled with them. He dropped the flags and returned to the vessel. But he started to feel dizzy and soon fell unconscious. So did Mr. Small.

When the mission’s operations crew was pulling up the vessel, they saw the unconscious men on a television feed and sent two divers to investigate. One of them was able to shut the vessel’s hatch after cutting away a piece of Mr. Keller’s flipper, which had become stuck between the door and its frame, allowing pressure to build inside the bell. The other diver went missing. His body was never found.

Mr. Keller revived while still inside the bell. Mr. Small woke up, too, but he was weak, thirsty and sleepy, and eventually Mr. Keller had to give him mouth-to-mouth resuscitation. Mr. Small died of decompression sickness before he could be transported to a hospital.

“The gas mixture had gone bad,” Ben Hellwarth wrote in “Sealab: America’s Forgotten Quest to Live and Work on the Ocean Floor (2012), adding that the disastrous dive “caused a sharp decline in interest in Keller’s sensational methods.”

The dive “was a milepost in the sense that it was the first time something like that had been done,” Christopher Swann, a diving historian, said in a phone interview. “But it was a failure, because one person died with him and another person disappeared.”

Mr. Keller died on Dec. 1 at a nursing home in Wallisellen, Switzerland, near his home in Niederglatt. He was 88.

His daughter Ethel Keller confirmed the death. She said he had been diagnosed with Covid-19 twice and had several infections.

Hannes Keller was born on Sept. 20, 1934, in Winterthur, Switzerland. His father, Friedrich, was an architect. His mother, Emma (Schneider) Keller, was a homemaker.

Hannes took university courses in mathematics and physics but did not graduate. He later taught math at a college.

He began diving in Swiss lakes in 1958, an experience that gave him a vision for the future.

“It quickly dawned on him that unlike space exploration,” Mr. Swann wrote in “The History of Oilfield Drilling: An Industrial Adventure” (2007), “diving was a field where an individual carrying out his own research could have a big impact, and that the way to do that was to break the world depth record.”

In 1959, Mr. Keller dove to 400 feet in Lake Zurich in a rig made out of a 50-gallon oil drum. He then trained at various depths in the compression chambers of an elite French underwater research group and the experimental diving unit of the United States Navy.

In late June 1961, Mr. Keller and a Life magazine writer, Kenneth MacLeish, dove to a record depth of 728 feet in Lake Maggiore, in Switzerland, on an elaborately built platform that let Mr. Keller experiment with his mixture of gases. At a depth of 350 feet, Mr. MacLeish wrote, Mr. Keller switched to a different mixture of gases he had designed for deeper water.

“There is barely enough ‘air’ to breathe, and it is bitter cold,” Mr. MacLeish wrote, “even colder than the ice water in which we now hover. My teeth itch. I try to say OK but cannot manage it. Still, it appears that I can live on what we are getting.”

Mr. Keller’s success at Lake Maggiore brought him financial support from the Navy. Shell Oil, which was interested in how his research could benefit its offshore oil drilling, provided the support ship for the Catalina dive.

Despite the deaths on that dive, Mr. Keller and Dr. Albert Buhlmann, the cardiopulmonary specialist who had helped Mr. Keller design his gas mixture, signed a contract in 1964 with Shell International Petroleum to continue their research.

“Hannes Keller’s prominence in the world of deep diving was relatively brief but definitely bold,” Mr. Hellwarth said in an email. “His thousand-foot dive turned into a Houdini-like spectacle, unfortunately with disastrous consequences.”

Mr. Keller moved on. In the late 1960s, he and a business partner, Hans Hess, developed a deep-sea diving suit and an aerodynamic ski-racing suit. Over the next few decades he started a line of computers, developed software programs and created an online art and photo museum.

In addition to his daughter Ethel, Mr. Keller is survived by another daughter, Leonie Keller; his sons, Fabian and Severin; and two grandchildren. His marriage to Tzuara Keller-Takahashi ended in divorce. His second wife, Esther (Frei) Keller, died in 2017.

The daring that Mr. Keller displayed in his diving could sometimes reshape itself into whimsy. In 1968, Mr. Keller, a classical pianist who occasionally appeared in concert, staged a benefit performance at a concert hall in Zurich starring a man he introduced as the Russian pianist Antonei Tartarov, who showed up onstage sporting a Beatles-like moptop and dressed in tails, a red tie, a red waistcoat and red socks. The program included what were said to be newly discovered works by Beethoven and Liszt.

Before the final number, Mr. Keller walked onstage to tell the audience that the performer was actually the Swiss pianist Jean-Jacques Hauser, who had improvised the “newly discovered” music.

“All except one Zurich critic were impressed by Mr. Hauser’s virtuosity and enjoyed the joke,” The New York Times wrote, adding, “Only one angry woman demanded her money back, and even she refused to take it when it was offered her, Mr. Keller said.”