At 7:30 on a Sunday morning the Good Time Diverleft Ocean City Marina bound for a wreck 20 miles offshore, 15 fathoms down -- 90 feet below the surface. Diving instructor Captain John Steffy stood at the helm of his converted oyster boat, guiding it through the channel and out to sea.

The first dive was to be the Port Hole, an oil tanker torpedoed by a U-boat in 1944.

Steffy says the most common question divers ask is about sharks. None, he said, have been seen on any wreck dives he can recall, though he recently saw a whale.

"I saw it break the surface, shoot its spout and go back under," he said, "but a diver on board saw the same whale just as it went under and thought it was a sea turtle.

"Different people see the same object differently -- like Chessie the sea creature. I think everyone would like to believe that it exists but technology is so good these days that for a species that large to go unnoticed for so long is unlikely," he said of the recent sea serpent report.

Steffy, who runs the Calypso Dive Shop in Kent Narrows, Maryland, says he once saw an unusual object in the Chesapeake while diving for oysters.

"The image was about 40 feet long and about 5 feet below the surface. It was moving sideways, but I knew it couldn't have been a telephone pole because of the way the current brushed against it. We went over to where the object was. It went under and I never saw it again."

With his hands and face, he made one of those "What was it?" expressions and said, "You just never know."

The Good Time Diver cruised steadily at 10 knots over an unusually calm Atlantic. The sun had risen in a cloudless sky, and 11 divers rested on deck.

"Visibility should be good today," Steffy said. "Sometimes it can be as high as 50 feet and other days as low as five feet."

In Steffy's two years of taking people on wreck dives off Ocean City, he has had no injuries or accidents to report, except for the time a three-inch bream bit a student on the lip, drawing blood.

TheGood Time Diveris anchored, instructions are given, and the divers in full wet suits back-drop and side-roll into the water. A short meeting at the anchor line, then down. Every few feet noses must be pinched. Down past the wall dividing warm and cold layers; from now on, the farther down, the colder the water.

The rusted oil tanker, covered with mussels -- some as big as four inches -- rests quietly on the ocean floor. Many of its portholes are missing; the few that remain have survived divers' efforts to take them home. Silver jacks, black sea bass and tautog swim in and about dark places of the ship. Large welk conch, ocean sea clams and other mollusks sit on the bottom. Half an hour and it's time to leave the casualty of World War II.

Back on board, divers empty their finds from the wreck dive: shells, star fish and an old Sea Hawk dive knife.

"That was fantastic," said a diver from Virginia. "Last week was my first deepwater dive. Today I was more relaxed and able to enjoy it more."

"It was quite a different sensation," said a first-time deepwater diver. "Passing through into the cold water is like entering a different world after crossing a thin line."

The Good Time Diver heads east for the day's second and final dive. In 1958, the African Queen went down during a winter storm. It rests between 60 and 70 feet, and in one spot it's 80 feet down. Dive tables must be studied to find out at what depth and for how long a diver can stay down without getting the bends.

For some, this dive's emphasis will be on dinner -- people are allowed to use spear guns to catch fish, but Steffy is sensitive about people spearing more than they can eat.

"Most people have a negative opinion of divers' using spear guns to catch fish," he said. "But it's actually a better way to do it, because you have to look at the fish when you shoot it. It makes it a bit more difficult and adds to your appreciation of the fish."

Sixty feet below, a tautog swims by. Its alternating shades of gray blend with the inside of the wreck. A diver holding his spear gun leads the fish by aiming at its head, shoots: a near-perfect hit, just behind the gills. In silence, the surprised and shocked tautog struggles to free itself. The diver secures his catch and swims on.

Twenty minutes pass, time to ascend. Several good-size tautogs have been speared, but no one has caught more than he or she can eat. The day before, Steffy said, divers brought in 15 lobsters. No lobster today, just lobster-tasting fish.

Heading home, divers relax, tired from the day's activities. Beer and sodas are passed around. Captain Steffy appears from the hull holding a pot-full of mussels steamed in wine.

"Oh no," he moans, "I forgot the butter."