Dan Taylor, who died July 23 at 65, was an indefatigable pursuer of the Loch Ness monster.

Often drawing comparisons to Captain Ahab, he sold his house to finance a submarine he built himself. Christened Nessa after a Gaelic water goddess, the craft was 44 feet long, painted electric yellow, and armed with special harpoons he called biopsy wands, designed to collect a skin sample for scientific analysis.

Taylor announced in January that he intended to make his first dive in the spring, but instead continued to tinker with the submarine at his rural Hardeeville, Ga., workshop. The project had been delayed for years, but he was unperturbed. “I see no other purpose for my life now but this expedition,” Taylor wrote in an online diary. “It will fulfill my aspirations and my promises.”

It was an obsession Taylor nursed for more than 35 years.

Had the spring dive occurred, it would have been Taylor’s second time searching for Nessie in the chilly loch waters in a home-built sub. In 1969, with funding from the World Book Encyclopedia, he made about 50 dives in a 20-foot fiberglass sub named Viperfish.

The Viperfish was unsuited to the task, being too slow to follow whatever jostled it 130 feet down on one intriguing dive. The expedition was plagued with problems. The Viperfish leaked so badly from the hatch that Taylor sometimes carried an umbrella while submerged.

Once, it even sank at its moorings.

Taylor finally called off the search in the fall of 1969, vowing to return in three years with a new submarine, one that could better deal with the 12-inch visibility of Loch Ness’s turbid waters. The years stretched to decades, but the itch to pursue the world’s most famous mystery of cryptozoology persisted.

Taylor was born June 19, 1940, in Memphis, Tenn. He studied engineering at the Georgia Institute of Technology and enlisted in the Navy in 1958. He served as a submarine torpedo man and participated in the blockade of Cuba.

Blessed with a modest independent income, he used his time to tinker with any number of mechanical projects, including windmill generators, a giant aquarium, and his own hydroelectric dam. Taylor’s first boat design, executed at age 7, was a bicycle outfitted with pontoons. It promptly sank. He had more success with the Viperfish, although it, too, fell far short of expectations. “Nothing I make ever works the first time,” he told the Los Angeles Times.

A bout of heart trouble in the mid-1990s convinced Taylor – a heavy smoker – that he should get serious about his return to Loch Ness. He sold his Atlanta home to raise money. His mother refused to help fund the project, although she did allow him, along with his wife, to move into her home.

The submarine slowly took shape at the Hardeeville workshop. It was a 44-foot steel tube, 6 feet in diameter, filled with electronics, and hydraulics, meant to hold four passengers, including a mission biologist. It weighed 35 tons and was designed to go as fast as 20 knots in short bursts, powered by a locomotive motor. “It’ll sound like a freight train a-comin’, but it’ll move like a freight train, too,” Taylor told Loren Coleman, a journalist and authority on cryptozoology. “This thing is going to be a cross between a research submarine and a locomotive, because that’s what it will take.”

The head of the Official Loch Ness Fan Club, Gary Campbell, protested when Taylor announced he would return to Scotland in spring, harpoon at the ready. “Nessie, along with all the other animals in and around Loch Ness, is protected under the Wildlife and Countryside Act, which is designed to stop madness like this,” Mr. Campbell told the Mirror newspaper of London.

Taylor’s spring timetable appeared to be overly optimistic. In the last entry to his Web diary, dated March 25, he reported “progress is good … we’re in the market for 30 plus air tanks. Don’t go diving without them!” This time, the delay would be permanent; this Ahab was denied the chance to go down with his leviathan.

Taylor’s death was reported by Scottish and British newspapers and on his Web site, nessaexpedition.com.