Liah had just turned sixteen and one day she noticed her hair was changing; once it touched the water it would become pink; she doesn’t want to be seen with pink hair so she went underwater to avoid people looking at her.
That’s when she notices she is able to breath under water with no problem whatsoever. And to her surprise she finds a dolphin named Zuma that she can talk to!
She is shocked and wants to know why this is happing to her and decides to begin searching.
Liah is scared because she doesn’t know what is happing in to her so she tells her grandfather Brake what she has been going through; he revels a secret that he has been keeping from Liah, he tell her mother is a mermaid named Calissa and that she rules in an underwater world named Oceania; and since their where many dangers their she gave him her baby so that she could grow up as a human and be safe.
A mermaid named Eris wanted to be more powerful than Clarissa so afraid that Eris would hurt her baby that was born in a human form and without a fin Clarissa gave her to Brake.
Liah can’t believe what she is hearing and runs away, while she is in the ocean Zuma appears and tells her everything her grandfather told her is true and that she is the princess of Oceania!
Zuma asks her for help, she tells her that she must go to the underwater kingdom, because Eris rules in a cruel and vicious way. So she must help them find the Queen and mother of Liah in order to defeat Eris!
The young mermaid decides to go to Oceania to save her mother and while she is there she is witness of the way the evil Eris rules and if some is to challenge her in any way they are sent to the whirlpool cell.
Zuma is always with Liah and she introduces two of her friends to Liah: The mermaids Kayla and Xylie who help her find a tail for her to put on and that way she won’t seem suspicious.
Eris is informed that Carissa’s daughter will soon arrive to her kingdom and that she has come to destroy her, so she must act quickly and finish with Liah before she loses control over her kingdom.
Meanwhile Liah turns to the fate mermaids they are small mermaids who are prophets and they tell Liah that if she wants to defeat Eris she must find a heavenly hair pin, a dream fish and the necklace that Eris wears her protecting necklace.
Once she has all this, she will them be able to take away the evil mermaids powers; so Liah and her friends begin the search ,they easily find the first two things, but they have to carefully plan a way for them to get Eris protecting necklace.
The mermaids are able to get the necklace, but nothing happens, Eris creates a huge whirlpool and put Liah in it and has no way out.
While Liah is in the whirlpool she is convinced that she is in fact a half Princess mermaid and is instantly turned into a real mermaid with enough power to trap Eris into one of those whirlpool cells.
Liah finds and frees her mother Clarissa, together they rebuild the damaged kingdom; her mother gives her a necklace that can change her into a mermaid any time she wants.
Liah returns to Malibu with her grandpa and wins the surfing competition. Everyone celebrates her victory including her mother!!