Jack O’Neill in 1982, suiting up in one of the wet suits that he helped popularize through the company O’Neill. (Dan Coyro/Santa Cruz Sentinel via AP)

When Jack O’Neill began surfing in San Francisco in the early 1950s, taking off during his lunch hour to plunge into the frigid, fog-covered waters of Ocean Beach with a balsa-wood board, he wore little more than a pair of bun-hugger swim trunks. On days when the sea dropped below 50 degrees, he donned a woman’s bathing cap and a pair of custom trunks lined with foam vinyl for insulation.

Mr. O’Neill, who died June 2 at 94, reveled in the thick-skinned culture of surfing’s postwar years, when he and his fellow watermen paddled until their skin turned blue and burned tires on the beach to warm up before heading back to work. But perhaps more than anyone else, he also helped to usher in a new era for the sport, one in which surfers from Malibu to Madeira can paddle for hours with little regard for the weather.

With the wet suit, a snug-fitting neoprene outfit that Mr. O’Neill popularized through a company that bears his name, he made surfing accessible to the many beachgoers who resist dipping a toe in chilly waters, let alone riding a board through strong winds.

“The wet suit itself got many more people in the water than any surfboard design in history,” said surfing historian Matt Warshaw. “You can’t surf if you’re purple and shivering.”

Mr. O’Neill, who for many years cultivated a piratical image by wearing an eye patch and sporting a well-salted, Hemingwayesque beard, was not the principal inventor of the wet suit. According to most accounts, including Warshaw’s “Encyclopedia of Surfing,” credit goes to Hugh Bradner, a physicist who worked on nuclear weapons as part of the Manhattan Project. In 1951, Bradner devised a rubber garment that promised to help Navy frogmen stay warm during their dives.

Mr. O'Neill lost vision in his left eye after a surfing accident in 1971. (Dan Coyro/AP)

One year later, a surfer named Bev Morgan began applying Bradner’s design for recreational use, making neoprene wet suits for scuba divers at the Scripps Institution of Oceanography in La Jolla, Calif.

Yet it is Mr. O’Neill who retains a singular identification with the outfit, in large part because of a marketing savvy that has helped his O’Neill wet-suit company become the largest wet-suit manufacturer in the world. Run by Mr. O’Neill’s son Pat since 1985, the business now claims to manufacture about 60 percent of the world’s wet suits.

In a statement, the company said Mr. O’Neill died at his seaside home in Santa Cruz, Calif., where he had installed an indoor trampoline and porthole windows in the basement. No cause of death was disclosed.

He had sold windows, skylights and parking meters before turning to surf gear in 1952, founding a store called the Surf Shop inside a San Francisco garage. Wet suits were at first an afterthought: “All my friends said, ‘O’Neill, you will sell to five friends on the beach and then you will be out of business,’ ” he once recalled.

Yet the neoprene vests and suits, which he said he was inspired to make after spotting the material on the floor of a DC-3 passenger plane, started to catch on after Mr. O’Neill began laminating a layer of nylon to the inside of the rubber. The adjustment made them more durable and more comfortable, prompting a now-ubiquitous company slogan: “It’s always summer on the inside.”

Mr. O’Neill’s marketing flair extended to trade shows, in which his children demonstrated the effectiveness of the wet suit by frolicking in tanks of ice water, and to everyday outings near the company’s headquarters in Santa Cruz. He raced across beaches in a land yacht, a type of wind-powered vehicle that he piloted himself and whose sail advertised his company’s shops. And he purchased a 65-foot catamaran to use as an “aircraft carrier,” allowing him to pilot and land hot-air balloons at sea.

When he lost vision in his left eye following a surfing accident in 1971, Mr. O’Neill embraced the resulting eye patch, using a likeness of his bearded, one-eyed face as a company logo. The injury was in part a result of another family invention, the surf leash, which Pat O’Neill had helped create one year earlier; when Mr. O’Neill lost his balance and fell off his board, which was attached to an ankle by his surf leash, the board bounced back and struck him in the eye.

Although the sale of wet suits made Mr. O’Neill a multimillionaire, he at times seemed to resent his business’s success, which caused many of his favorite beaches to become crowded and sometimes kept him away from the water for extended intervals.

“The business just takes too much time,” he told Surfer magazine in 1972. “There’s too much paperwork and talking to bankers. If I had it to do over again, I think I might stay with commercial fishing.”

Mr. O’Neill was born in Denver on March 27, 1923, and grew up in Long Beach, Calif., where he learned to body surf at the city’s horseshoe-shaped Rainbow Pier.

He served in the Navy during World War II, and in 1949 he received a bachelor’s degree in business administration from the University of Portland in Oregon.

With his wife, the former Marjorie Bennett, he moved to San Francisco in the early 1950s. She died in 1972, and a son, Mike, died in 2012. Survivors include his wife Noriko; six children from his first marriage, Cathi, Bridget, Shawne, Pat, Tim and Jack Jr.; and six grandchildren.

Mr. O’Neill relocated to Santa Cruz in 1959, drawn by the promise of better waves and warmer waters. He remained in the city for the rest of his life and in 1996 created O’Neill Sea Odyssey, an environmental organization that has introduced nearly 100,000 grade-school students to marine science and ecology. The program’s highlight is a trip aboard Mr. O’Neill’s old aircraft carrier, now without balloons, to explore the Monterey Bay National Marine Sanctuary.

“The ocean is alive and we’ve got to take care of it,” Mr. O’Neill once said. “There’s no doubt in my mind that the O’Neill Sea Odyssey is the best thing I’ve ever done.”

Correction: An earlier version of this obituary incorrectly said that Jack O’Neill’s seaside home was in Santa Barbara, Calif.