With a treasure trove of publicity awaiting them on shore, the explorers of the Andrea Doria expedition, who for one month have been diving to that sunken ship, returned triumphantly to land this morning to proclaim their journey a grand success.

They had discovered the reason the great ocean liner, once called unsinkable, had gone to the bottom so quickly. (It had a giant hole in it.) They had raised a safe -- perhaps containing up to $3 million, probably not -- and claimed it as their own.

The documentary they had made of their expedition, for which leader Peter Gimbel had previously been unable to find a sponsor, was now eagerly being sought. A Budweiser commercial crew was coming to film. Nothing, it seems, so captures the heart of modern man as sunken treasure, whether or not it exists. Even a U.S. Customs man, Dennis Murphy, eying the rusted safe in its water-packed crate at the bow of the ship, could not withold a wistful remark.

"Really sexy," he said. "A safe from the Andrea Doria finally making it to New York."

The leaders of the expedition, Gimbel and his wife, Elga Andersen, have stressed from the beginning that theirs was not a treasure hunt.

It was apparent this morning, however, that they did not underestimate the value of the safe, either. New York state troopers with a helicopter were at the Montauk dock, awaiting word to escort the safe, after its photo session, to New York City. At the New York City line, city police were to take over.

The safe was not opened. From the outset, Gimbel and Andersen have planned to crack it at the end of their documentary on live TV. Until that time, to protect it from the possibly damaging effects of the air, it will be immersed in water. The water (clearly Gimbel and Andersen have a genius for this kind of thing) will be in the New York Aquarium shark tank.

Whether the safe, taken from the purser's office in the first-class lounge, contains treasure seems less and less likely.

An admiralty attorney, James M. Estabrook, retained by Gimbel for the occasion -- "I'm here to slap an injunction on anyone who tries to lay claim" -- confessed on shore this morning that he doubted the existence of substantial treasure. He also seemed in a position to know, having represented, in the last legal go-round, the ship Stockholm, which 25 years ago rammed the Doria. ("It wasn't the Stockholm's fault?" someone asked. "Pleeease," said the attorney, with a look of theatrical hurt.)

The contents of the safe, he continued, were to the best of his knowledge, scant. The ship's purser, according to his log, had returned almost all of the valuables to the passengers the evening of the crash. The ship, after all, was due to arrive in New York the next day. The Bank of Rome, which had a small branch office on the ship, received $20,000 for its claim. The unexpected, of course, was always possible.

"There could be shipments we don't know about, sometimes people ship diamonds parcel post," he said.

An attorney from U.S. Customs, Mel Minsky, speaking from his own professional experiences, had another thought.

"Could be 30 pounds of heroin," he said.

Both lawyers agreed that, under international law, the contents of the safe were Gimbel's; to the salvager, they agreed, went the spoils.

But a spokesman for Customs, which had, this morning, at least four people in attendance, said that Gimbel would certainly have to pay duty on the safe's contents, explaining that since the contents would not be known until the safe was opened, Gimbel had posted a $2 million bond for its worth. Gimbel would also be required to pay duty on the china and other artifacts brought from the ship, according to Customs spokesman Murphy.

"We treat it just like any foreign merchandise," he said.

The expedition, whose offshore oil vessel had anchored directly above the wreck of the Andrea Doria, had consisted of 30 persons: film-makers, commercial divers, and seamen.

It had been an expedition, for both sailors and divers, beset by difficulties. At one time, catching the end of Hurricane Dennis, the expedition ship had been buffeted by 15-foot waves. To the divers, who spent their off hours in a small pressurized chamber, the experience was frightening as well as uncomfortable.

"For two or three days I was stuck in that thing the compression chamber while the waves battered the ship. It was scary and worse than diving," 43-year-old diver Bob Hollis told United Press International.

He also said that the dive to the ship, which lay on its side in a shroud of fisherman's nets at a depth of 230 feet, was often unsettling. The ship on its side, said Hollis, gave an impression of a world that was "sideways," a desolate "grand hotel" in which he could sometimes envision well-dressed men and women. The lines, swift currents and poor visibility made the dive frightening.

It was also, he said, thrilling.

"You don't want to quit," he said.

On Tuesday, before the expedition vessel weighed anchor, Gimbel, who has been diving himself, and Andersen, who also dived, decided to give everyone an opportunity to see the ship. The cook, Jim Olivia, a hefty man with Hell's Angels tattoos on his knuckles, put them up to it. "Aaawh, c'mon, gotta let 'em down one time. C'mon, when are ya gonna give 'em the joy ride," he said.

Gimbel and Andersen agreed, and when the last team of divers was finished, engineers, the first mate, even the Sea Level 11's skipper -- most of them Louisiana men who had never put on a diving suit -- lined up to descend in the bell.

"Sensational, just sensational," said assistant engineer Tom Uhl, who, despite a career at sea, has never been beneath the surface.

"First you see the water rippling around the bell -- that's kind of an eerie feeling, because you know if anything happened, you could just kiss it goodbye -- you see all kinds of fish, then you see the outside of the hull . . . all kinds of parts gone; you could see the exhaust vent on the stack, you could see the barnacles . . . it all lasted maybe five minutes . . . but now, like we all said, we can all say we were there . . . . "