The female calf was found in the Gulf of Mexico, near Venice, and rescued by Mote Marine Laboratory and the Florida Fish and Wildlife Conservation Commission.
Rescuers brought the baby to ZooTampa's Manatee Critical Care Center.
Staff say the calf weighed in at just 44 pounds.
ZooTampa's Manatee Critical Care Center is one of only two places that takes in orphaned manatee calves, the facility said.
Earlier this month, SeaWorld Orlando took in two orphaned manatee calves, and said the tiny animals need around-the-clock care, getting bottle-fed every three hours.
According to SeaWorld, manatees must grow to about 600 pounds before they are ready to be released back into the wild.