Felix Braves the Briny is a 1926 Felix the Cat short produced by Pat Sullivan.
Plot[]
Felix hears an old sailor talking about a hidden treasure chest and plans to retrieve it from the bottom of the sea. The old pirate and his crew set sail on their treasure hunt on the high seas, and Felix the cat follows them in a submarine he has improvised from a barrel. There, seventy fathoms underwater, the daring black cat fights off sharks and the diver sent by the pirates. Felix finds the buried gold, but is caught by a captain. He makes a deal with the captain and everything ends as it should.