Barbie in A Mermaid Tale is about a sixteen-year-old girl called Merliah Summers, (Liah for short). She is a top surfer at Malibu and is nicknamed, "Queen of the waves". On the day of a surfing competition, Merliah is surfing mavericks, when one part of her hair suddenly turns pink on contact with seawater. Nervous of showing everyone her hair, she dives underwater and meets a pink-ish purple coloured, dolphin named Zuma. When the Zuma talked Merliah gasps but finds out that she can breathe underwater. Zuma takes Merliah to her friends then disappears. Merliah tells her friends Fallon and Hadley what happened, then she goes home, confused. After telling what happened to her grandfather, Break, Merliah finds out that she is half-mermaid. Thinking that her parents died when she was a small baby, Merliah's grandfather tells her the truth. Break tells her that Merliah's father was a human named Rip and that her mother was a mermaid named Calissa (who in fact, is the Queen of Oceana).Break tells her that when Merliah's father died, Calissa was worried about the fact that Calissa's evil mermaid sister Eris would try to rule over. At the same time, Calissa gave birth to Merliah. Merliah had no mermaid fins which made it dangerous for her in Oceana. Calissa didn't want Merliah to get hurt, so she took Merliah to her husband's father, Break (Merliah's grandfather). Calissa asked if Break could raise Merliah so that she would be safer on land from Eris's rule. It worked. Then Eris took over and Break told her that Calissa had died or was in Eris's rule. At first, Merliah didn't believe Break and left to tell her friends the news.