The West Indian Manatee (Trichechus manatus) is the largest surviving member of the order Sirenia. They are thought to have been mistaken for mermaids by sailors who had been at sea for too long. Threats to the West Indian Manatee include habitat loss, and injury and death due to commercial and recreational boating.
For more on West Indian Manatees go to:
http://www.savethemanatee.org/manfcts.htm
http://www.arkive.org/west-indian-manatee/trichechus-manatus/
http://kids.nationalgeographic.com/kids/animals/creaturefeature/west-indian-manatee/