On command, Cooley, a black Labrador, hurls herself into the Gulf of Mexico and vanishes into the depths. Aboard the ketch Gamboleer, anchored in 30 feet of water off Destin, Fla., all is silence, save for the wind in the luffing sails. Suddenly a black muzzle breaks the surface. Cooley, clutching in her jaws a sand dollar she has fetched from the bottom, paddles over and clambers aboard. "She's a real scavenger of the deep," says her proud owner, red-bearded Randy Gibson, 32. "She's not afraid of anything."

As the only diving dog in the Florida panhandle, the 3-year-old Cooley has become a partner in Gibson's $100,000 business in jewelry and novelties—many of them crafted from her undersea haul.

From March to October, when sand dollars are most available, Cooley brings up some 30 a day. Once dried, the pie-shaped shells are either gold-plated or hand-painted with Florida landscapes by Gibson's parents, then put on sale in area restaurants for up to $15 apiece. Gibson's competition collects sand dollars by the costlier method of dragging shrimp nets.

A retriever by breed, Cooley used to fetch Frisbees that her owner threw overboard. Then Gibson filled one with sand and let it sink to the bottom. To his surprise, Cooley went after it. She quickly learned to hold her breath going down and exhale as she rose. Even when Gibson buried a Frisbee on the gulf's bottom, Cooley dug it up and brought it back. "After that," says Gibson, "sand dollars were a cinch—they're brown and only partly covered with white sand."

Not even maternity has quenched Cooley's enthusiasm. After whelping a litter of eight pure-bred pups early this spring, she is diving again, her muzzle and paws stained from the iodine-saturated sand dollars. She has never been bothered by sharks, and Gibson is careful not to take her into more southerly waters, where she might be tempted to bite down on spiny sea urchins. (Cooley did return once with a rusty fishing rod.)

Gibson has come closer to disaster than his dog. Twice, while trying to swim ashore at night during beer parties, he faltered and the loyal Labrador came to his rescue. "The shore looked much closer than it was," Gibson explains. "When I got short of breath, I had to grab her collar. She pulled me right along."

The dog's diving act has so impressed officials of the Gulfarium in Fort Walton Beach that they have inquired about using her in exhibitions with their dolphins. "She'd take right to it," says Gibson. "We may just strike a deal." As her agent, he's considering $50 to $100 for three shows a day. Meanwhile, Gibson, Cooley, a sedentary Irish setter named Radar and a parrot called Little Bit continue plying the gulf aboard Gamboleer.

Once a prelaw student at Florida State, Gibson dropped out in 1970 to pursue life as a craftsman. He spent two years converting brass-fitted hatch covers into coffee tables, then bought and salvaged the 37-foot Gamboleer after the boat had been half destroyed in a hurricane. He purchased and restored an abandoned hotel five miles east of Destin, and lives just north of town in the oldest house on Okaloosa Island. He keeps his unorthodox collection of vintage automobiles there—six 1948 Plymouth Deluxe sedans.

Tourists think Gibson looks like a pirate, and he does not discourage the notion. It's good for his handcrafted jewelry business (appropriately named Salty Dog), and it allows him to indulge one of his fantasies. As a boy growing up in Pensacola, he often heard tales of Billy Bowlegs—who preyed on English and Spanish ships off the panhandle in the 18th century—and of Redbeard, the Barbary buccaneer. "Redbeard, that's the one I look like," says Gibson. "But Redbeard never had a diving dog. To me, she's worth more than all the doubloons of the Spanish fleet."