Costa Rican officials say 86 shipwrecked migrants have been rescued after fishermen found a message in a bottle they had thrown overboard.
The boat had been adrift off the island for three days (Photo: MarViva/ACMIC)
The migrants, mainly teenagers from Ecuador and Peru, had been adrift in their packed boat for three days.
The vessel had been floating near Cocos Island, a nature reserve 600km (372 miles) off the Costa Rican coast.
It is believed that the group were abandoned by people smugglers when the vessel got into trouble.
The smugglers stripped the boat of radio and communication equipment when they left it.
"Incredibly [...] these people, who are quite young, wrote a message saying: 'Please Help Us' and put it in a bottle," said Francisco Estrada of marine protection group MarViva.
The bottle, and the SOS message it contained, was found by local fishermen who alerted the park wardens, the only inhabitants of the island, a world heritage site.
The wardens then told MarViva who were able to rescue the group, which included women and children.
The group was hoping to reach Guatemala, from where they wanted to cross the border to Mexico, according to a spokesperson for Costa Rica's public security ministry.
The migrants are now on the island and awaiting the arrival of a ship with food and medical supplies.
Many of them are suffering from dehydration and sea-sickness.
A doctor and an immigration official are also being sent to the island.