Factual error: Sharks don't float when they're dead, they sink. While it did initially sink after being thrown out of the "casket", when the shot changes to Don Lino and Lenny consoling one another, you see him float back up. (00:33:50)
Factual error: The "Mafia" characters are shown being on the Titanic (the life preserver behind the coffin during the funeral reads R.M.S. Titanic in its trademark red and white logos, with the white star company printed on its side) but the other fish in the movie are warm-water fish that live on a reef. The Titanic sank in the north Atlantic, how is there a warm-water reef nearby?
Answer: That's for you to interpret, but most likely she went swimming away screaming in terror, being chased by a crazy fish. Think "My Crazy Ex-Boyfriend" premise.