Merman Mariano hails from the lost city of Atlantis, which is not too far froma sprawling coral reef. The coral reef is home to amazing creatures like the blue parrotfish, angelfish, and even the nurse shark. One of the main sources of food for the Atlanteansis the algae that grows on coral. Unfortunately, the coral supply is depletingand it's up to Merman Mariano to figure out what'sgoing on and how to stop it! While on his coral quest, Mariano meets Mermaid Tasha. With her help, Mariano comes to land to teach the humans what they can do to protect the reefs by being responsible divers and fishermen, using reef-save sunscreen, and recycling.