“We were alerted to them by the flags that they actually had in addition to a large cross that they put out there for themselves,” helicopter pilot Mike Allert told WPLG.
Allert said he decided to fly back around Anguilla Cay to investigate and a crew returned to the island later Monday to drop water, food and a radio.
The trio was stranded on an uninhabited Bahamian island between Key West and Cuba, the agency posted on Twitter.
A helicopter crew returned Tuesday to pick them up.
Coast Guard officials tweeted that the trio was from Cuba. They told officials their boat had capsized in rough waters and they were able to swim to the island.
The trio told the crew they had survived on coconuts, conchs and rats, news outlets reported.
It was not immediately clear whether they were migrants attempting to come to the United States, or if they were just lost at sea, U.S. Coast Guard Petty Officer 2nd Class Brandon Murray told the South Florida SunSentinel.
They were taken to the Lower Keys Medical Center, where none appeared to have serious injuries.
“I cannot recall a time that we saved people who were stranded for over a month on an island,” he told the newspaper. “That is a new one for me.”