Merliah was born half-human and half-mermaid. She was born in Oceana, an underwater kingdom, ruled by her mother Queen Calissa, but her father was just a usual human. When she was just a little baby, her mother gave her to Rip's father, Break, because she was born with legs and couldn't live in Oceana.
When growing up, Break thought Merliah couldn't handle the facts. He had told her that her parents died when she was a baby. She grew up as "super-surf champion". She also has two friends named Fallon and Hadley, and the trio loved to surf and Merliah was one of the competitors of the team Malibu. She always won every surfing competition, and that's why she is nicknamed the Queen of The Waves. She even had no idea about her origins and thought that she was a normal teenager, when she was really a mermaid princess and the daughter of the Pacific ocean's queen.
One day, when she was in a surfing contest, her hair unexpectedly turned pink and she was able to breath underwater, and she was surprised to hear a pink, sparkly dolphin named Zuma talking. When she got home, Break told her the truth about her past, but she doesn't believe it. But when Zuma tells her that everything Break told her was true, she yanks off the magical necklace given to her as a baby, it was revealed that her mother was alive. So she comes with Zuma to Oceana, but just to see her mother to change her back to just a "normal" girl. Over the course of her adventure, however, she starts to accept her mermaid half. Merliah learns that, what makes you different may be your greatest strength.