In 1969, when he was 28, Dan Taylor plumbed the stygian depths of Scotland's Loch Ness in a homemade yellow submarine, seeking the fabled monster. Now, nearly 30 years later, he has had a heart attack and a stroke—and what is he doing? He's building another yellow submarine—bigger, stronger, more modern—in his workshop in Hardeeville, S.C. He'll be heading back to Loch Ness next summer. "The only way to find out what Nessie is," says Taylor, 58, a retired telephone technician, "is to go down there, catch up with her and get a biopsy and a photo." If he spots anything, Taylor plans to shoot darts from the sub's bow and, he hopes, gather tissue so scientists can identify the elusive beast once and for all.

The scion of a wealthy Memphis family, Taylor—who resides in Hilton Head, S.C., with his long-suffering wife, Margaret, 64, a retired teacher, and mother Justine, 84—is a lifelong tinkerer and inventor. He built the first sub in his backyard, then volunteered his services to a team of scientists investigating Nessie. The new, 31-ton sub could cost as much as $1 million, and Taylor, who is looking for a sponsor, has financed it out of his own pocket so far. "You read about guys my age who drop dead—I'm just going to make sure I've got everything I want done," he says. "But I'll probably get so excited down there, I'll have a heart attack anyway."

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