Barbie (Kelly Sheridan) isn't quite feeling herself today. In fact, she feels more like Merliah, a Malibu surf champ who's discovered that she's actually a mermaid in a girl's body. With her dolphin pal, Zuma, Merliah journeys to rescue her mom, the Queen of Oceana. Their adventures take them deep beneath the sea to a magical kingdom, where Merliah helps her fellow mermaids save the day and learns a valuable lesson in the process.