US Coast Guard officials are searching for 39 people who are feared missing after their ship capsized on Saturday night off the Florida coast.
Officials were alerted on Tuesday morning after fishermen spotted a man clinging to the hull of a boat 45 miles (72km) from the city of Fort Pierce.
The survivor said the group had embarked from Bimini, Bahamas, on Saturday night and hit foul weather.
US officials say the boat may have been part of a "human smuggling venture".
According to the survivor, who has not been identified, none of the passengers were wearing life vests.