| Director | Arthur Lubin, Robert McKimson |
|---|---|
| Genre | fantasy film |
| Runtime | 102 min |
| Country | United States |
The story begins in 1963, where George Stickle (a naval officer) and Admiral Harlock discuss how porpoises in the ocean are displaying unique characteristics and suspect that a former top-secret asset, Henry Limpet, may be teaching the creatures these abilities.
The story flashes back to September 1941 just before the attack on Pearl Harbor. Henry Limpet, a shy bookkeeper, loves fish with a passion and wishes he could be one. His friend George Stickle is a machinist's mate in the United States Navy. Limpet's wife Bessie is fiercely patriotic and Limpet tries to enlist but he is rejected, classified as 4F because of his poor eyesight and other reasons.
While George is on leave, he visits Limpet and Bessie, and they go to Coney Island, where Limpet falls into the water and turns into a fish for unexplained reasons. Since he never resurfaces nor can he swim, Bessie and George assume he has drowned.
The fish Limpet, complete with his signature pince-nez spectacles, discovers a new-found ability during some of his initial misadventures: a powerful underwater roar, his "thrum". He makes friends with Crusty, a misanthropic hermit crab. After saving a female fish he names Ladyfish (the concept of names being unknown to her), he falls in love with her despite already being married.
After the attack on Pearl Harbor, Limpet directs a Navy convoy to a nearby German U-boat. Determined to help the Navy on an ongoing basis, Limpet contacts the convoy and requests to see George. With George's help, Limpet gets himself commissioned by the Navy, complete with an advanced rank and a salary, which he sends to Bessie. He helps the Navy locate Nazi U-boats 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 U-boats by redirecting their torpedoes. After the battle, he swims to Coney Island to say goodbye to Bessie, who gives him a replacement set of glasses. He then swims off with Ladyfish.
In the film's coda, back in 1963, George and the Admiral travel out to sea to contact Limpet about whether he is training the porpoises.