But they knew exactly what to do. They used lifejackets to signal for help and spelled out a huge "help" sign from dark palm fronds on the white sand.

For three days they sat and waited for rescue to come.

The US Coast Guard was notified of their disappearance on Tuesday, relaying an urgent message to shipping in the area.

They were finally spotted - thanks to their signs - on Thursday morning by the crew of a US Navy plane.