Some TV versions includes a longer version of the theme tune at the end.
ABC cut 15 minutes from this film for its 1986 network television premiere.
One TV version uses an alternate take of Madison entering a sunken ship; it's shown in long shot instead of the close-up of Daryl Hannah in the theatrical version. This is because Hannah's nipples can clearly be seen in that shot. Another take is used during the climactic underwater sequence for the same reason.
Some versions cut out the part where Freddie talks in Swedish to the guard.
A scene where Madison meets an elderly, ugly mermaid - the Sea Hag - who warns her of falling in love with a human, was filmed but dropped before the film was released. Short parts of this complex scene can be seen on the DVD.