Therefore, the agency has proposed downgrading the underwater grass-eaters to "threatened."
Under federal law, an endangered species is "currently in danger of extinction throughout all or a significant portion of its range."
A threatened species "is likely to become endangered within the foreseeable future," the FWS said.
The proposal is open to public comments until April 7.
Manatees feed on sea grasses and must come above water to breathe every 15 minutes or so.
They can reach 13 feet (four meters) in length and weigh up to 1,300 pounds (600 kilograms).
Their lifespan tends to be about 40 years.
Some conservation groups, such as the Save The Manatee Club, oppose the idea of downgrading the creatures' status because they say many threats still remain, and death counts have been high in recent years.
From 2010-2013, 2,441 manatees died in Florida waters, Save the Manatee Club said.