Queen Nerissa, known by her human disguise Chelsea Van Der Zee, is an evil Mermaid Queen disguised as a human teenager name Chelsea. She is 16 years old. She is the newest and most popular student at Oceanside High School. Queen Nerissa is incredibly manipulative and will step over anyone while lying to them on her way to the top. But she hides her evil side so she acts kind and sweet to others. She turns into a mermaid when she goes into the water and she has her own trident.