Splash, Too (1988)
Allen becomes bored on the deserted island on which he and Madison are currently living, and using a special power, Madison shows him exactly what's going on in his brother, Freddie's life. Through this, the couple realise that Allen's business is in trouble and return to New York - maybe contradicting the original, but Madison will only go "as long as I can soak my legs in Salty Water at the full moon". While there, they move into a new home (which has a pool in the back yard !), and Madison meets a new friend - Fern Hooten who might and might not know her secret. We are never told. While there, Madison sets herself a goal to save her Dolphin friend (Salty) who is in captivity, and while saving the business and the dolphin, she and Allen grow closer and re-kindle their love.
Tagline: Four years ago, a man and a mermaid swam away with your heart. Look who's back making waves. Splash, Too. A romantic tail.