Manatees are part of the order Sirenia, which are large, herbivorous mammals that live exclusively in an aquatic environment. The families include Trichechidae with three species living in fresh water habitats, the Amazonian manatee (Trichechus inunguis), the West Indian manatee (Trichechus manatus), and the West African manatee (Trichechus senegalensis). The dugong (Dugong dugon), is part of the Dugongidae, and technically not a manatee, which is restricted to the coastal and marine habitats from the Red Sea to Vanuatu that support seagrass meadows.

Whereas manatees have a round-shaped fluke, dugongs show a tail that is similar to other marine mammal species. Sirenians are well-known for being connected with the mermaid legend and are often the target of tourism activities.