The US Coast Guard said its crews had recovered one body and were continuing to search for 38 other people in the ocean off Florida days after their boat left the Bahamas in a suspected human smuggling attempt.

Captain Jo-Ann F Burdian told a news conference that finding the other migrants alive was the agency’s highest priority.

“It is dire. The longer they remain in the water … exposed to the marine environment … with every moment that passes, it becomes much more dire and more unlikely” that survivors would be found, she said.

US Coast Guard Captain Jo-Ann F Burdian
US Coast Guard Captain Jo-Ann F Burdian (Marta Lavandier/AP)

Search teams worked through the night after the crew of a merchant vessel spotted a solitary survivor on Tuesday morning clinging to the overturned hull of a 25-foot-long boat about 40 miles (64km) off Fort Pierce, Florida, she said.

Crews on at least four ships and five aircraft had already scanned an area about the size of Rhode Island, Capt Burdian said. They planned to continue searching throughout Wednesday before re-evaluating.

“We are using every piece of information we can to make sure we are exhausting our search efforts,” Capt Burdian said. “But we can’t search forever.”

The man told a good Samaritan who rescued him that he was part of a group of 40 people who left the island of Bimini in the Bahamas on Saturday night in what the maritime security agency suspects was a human smuggling operation. He said no-one wore life jackets as they capsized in severe weather.

The crew of US Coast Guard Cutter Ibis search for people missing from the boat
The crew of US Coast Guard Cutter Ibis search for people missing from the boat (US Coast Guard via AP)

The US Coast Guard said a small craft advisory had been issued as a severe cold front blew through the dangerous passage on Saturday and Sunday, with winds up to 23mph (37kph) and swells up to nine feet (three metres) high.

Tommy Sewell, a local bonefishing guide, said there were high winds and fierce squalls of rain on Sunday into Monday.

The survivor was taken to a hospital with symptoms of dehydration and sun exposure after he was found early on Tuesday sitting on the hull 45 miles (72km) east of Fort Pierce, the agency reported.

The US Coast Guard did not immediately describe the nationality of the survivor or the people lost at sea.

Migrants have long used the islands of the Bahamas as a stepping stone to reach Florida and the United States. They typically try to take advantage of breaks in the weather to make the crossing, but the vessels are often dangerously overloaded and prone to capsizing. There have been thousands of deaths over the years.

Crew members of the Coast Guard vessel William Flores, in Miami Beach, Florida, prepare to go on patrol
Crew members on Coast Guard vessel William Flores, in Miami Beach, Florida, prepare to go on patrol (Marta Lavandier/AP)

For the most part, these migrants are from Haiti and Cuba, but the Royal Bahamas Defence Force has reported apprehending migrants from other parts of the world, including from Colombia and Ecuador earlier this month.

The US Coast Guard constantly patrols the waters around Haiti, the Dominican Republic, Cuba and the Bahamas.

On Friday, its crews pulled 88 Haitians from an overloaded sail freighter west of Great Inagua, Bahamas.

“Navigating the Florida Straits, Windward and Mona Passages … is extremely dangerous and can result in loss of life,” the US Coast Guard said last weekend.

Last July, the agency rescued 13 people after their boat capsized off of Key West as Tropical Storm Elsa approached.

The survivors said they had left Cuba with 22 people aboard. Nine went missing in the water.