Barbie, a teenage princess, returns to the underwater kingdom to compete in a surfing tournament. Along the way, she discovers that an evil mermaid is planning to take over the kingdom. With the help of her magic powers and her friends, Barbie must find the courage to stop the evil mermaid and save the underwater kingdom.

Barbie, a mermaid princess, embarks on a mission to rescue her friend and discover a hidden undersea kingdom. Along the way, she faces challenges and fights against an undersea ruler. With the help of her friends and her responsibility, Barbie searches for a comb that will unlock the secrets of the underwater world and reunite her with her friend.