Manama, Bahrain ? Some worried passengers left a traditional dhow-turned-pleasure boat because it was swaying precariously.

That was before it left on a cruise that ended with the vessel flipping over, drowning 57 people, a British survivor said Saturday.

The dhow, an ancient form of sailboat used in the Gulf, had a permit only for use as a floating restaurant, not for passenger cruises, an Interior Ministry spokesman said. The spokesman, Col. Tariq al-Hassan, also said the boat’s captain, who has been detained for questioning, was not licensed to pilot the craft.

Simon Hill, who survived the capsizing, said the boat was swaying even before it left shore, and 16 uneasy passengers disembarked. He said a representative from the tour operator urged people to move below deck to distribute weight more evenly.

“We asked the captain if he was happy to leave, and if he wasn’t he should say so, and we would not leave. At 8 o’clock we sailed,” Hill told a news conference in Manama.

The dead from Thursday night’s accident included 21 Indians and 15 Britons, including a number of executives involved in the construction of Bahrain’s World Trade Center, a nearly completed complex of two 50-story skyscrapers in the shape of sails that are to be the tiny Gulf island nation’s tallest buildings.

The construction firm Murray & Roberts Group had rented the dhow, the Al-Dana, for a party celebrating the towers’ construction. But during the cruise, the craft tipped, sending people who had been dancing on the upper deck sliding into the water. It then flipped entirely, trapping passengers on the lower deck.

Hill, a manager with the construction firm, said the Gulf waters were calm during the cruise. About a half-mile from shore, he said, the boat made a U-turn to head back.

“It was a pleasant evening. And then in seconds, it went very quickly,” he said.

“I looked and I saw people sliding down the boat to one side, through the gap, and before I knew it I was in the water, under the water, and there were people everywhere in the water,” he said.

Those who were on the top deck swam away. But about half the passengers were below deck, some of them trying to smash the glass windows underwater, Hill said.

“We didn’t see anyone that was underneath come out,” he said.