Princess Lena is a beautiful adventurous mermaid who lives with her royal family in a watery castle. She has everything she could ever need including a mischievous pet dolphin named Vink but longs for only one thing to explore the world of humans. When a whirlpool takes her to the surface she sees and falls for the handsome Prince Stetan leading him to safety and vowing to return as a human. She is determined to marry the Prince but the only one who can replace her tail with legs is the evil sea witch Cassandra who promises to return her into a human. for a heavy price. Lena must give the witch her lovely voice and if the Prince marries another girl Lena will turn into seas foam.