The near-fatal collision with a boat two weeks ago left the marine mammal bloody and split open in the back with a part of her tail missing, the St. Petersburg (Fla.) Times reported Thursday.
Florida Fish and Wildlife Conservation Commission officials said it was not the first time the animal had been hit; they recognized her from scars left from previous incidents.
Ray Ball, director of medical sciences at the Lowry Park Zoo, said the tail wound was catastrophic, exposing vertebrae and causing a slow infection, anemia and pneumonia.
In the wild she would have died, zoo officials said.
Zookeepers have been using cloths soaked in a sugar solution to clean the manatee's infected wound.
Her recovery could be a long one, Ball said, but she is expected to survive.
"She's shown a lot of resilience," Ball said. "I'm actually a lot more optimistic than when she first came in."