Oceans of Love (1956)

The fish in the ocean seem to be making fun of an earnest young man in a row- boat holding a fishing line. A shark comes along, grabs the bait and the hook, and soon wrecks the boat. It's a close race as both head for the shore. The fisherman gets conked on the head and dreams of rescuing a mermaid from the denizens of the deep. As she is about to prove how grateful she is he wakes up to find the shark waiting to pursue him even on shore.