Splash
Tom Hanks was a relatively unknown TV actor with a sitcom as his biggest credit when relatively unknown director Ron Howard (best known for his own sitcom acting) cast him in this surprise hit. It made stars of Hanks, Daryl Hannah, and John Candy and an A-list director out of Howard. Hannah is a mermaid who comes to Manhattan in search of Hanks, the guy she has twice saved from drowning. Hanks runs a business with his lovable blowhard brother (Candy), whose goal in life is to have a letter published in Penthouse.