Join Barbie and her sisters Skipper, Stacie and Chelsea in this magical underwater adventure! While visiting Ken at his summer internship on a tropical island, Barbie and her sisters explore the wonders of the coral reef and discover a rare gemstone dolphin trapped in an enclosure. They soon meet Isla, a mysterious new friend who just so happens to be a magical mermaid. With the help of Isla, Barbie and her sisters try to rescue the gemstone dolphin from captivity and save the coral reef.