The Incredible Mr. Limpet

The Incredible Mr. Limpet is a 1964 American liveactionanimated adventure film from Warner Bros. It is about a man named Henry Limpet who turns into a talking fish resembling a tilefish and helps the U.S. Navy locate and destroy Nazi submarines. Don Knotts plays the title character. The live action was directed by Arthur Lubin, while the animation was directed by Bill Tytla, Robert McKimson, Hawley Pratt, and Gerry Chiniquy. Music includes songs by Sammy Fain, in collaboration with Harold Adamson, including I Wish I Were a Fish, Be Careful How You Wish, and Deep Rapture.

The fish Limpet, complete with his signature pincenez spectacles, discovers a newfound ability during some of his initial misadventures, a powerful underwater roar, his thrum. He falls in love with a female fish he names Ladyfish, and makes friends with a misanthropic hermit crab named Crusty.Still determined to help the Navy, Limpet finds a convoy and requests to see one of his friends, George Stickle. With Georges help, Limpet gets himself commissioned by the Navy, complete with advancing rank and a salary, which he sends to Bessie. He helps the Navy locate Nazi Uboats by signaling with his thrum, and plays a large part in the Allied victory in the Battle of the Atlantic. In his final mission, he is nearly killed when the Nazis develop a thrum seeking torpedo, and is further handicapped by the loss of his spectacles. He manages to survive using Crusty as his navigator, and sinks a number of Uboats by redirecting the torpedoes. After the battle, he swims to Coney Island to say goodbye to Bessie who has now fallen in love with George and get a replacement set of glasses. He then swims off with Ladyfish. ........

Source: Wikipedia