This is a story about four friends that are in the school swim team and are a secret scuba diving squad that help their school swim coach (who is a secret merman) move a hidden treasure chest that treasure hunters are looking for. However, if the treasure chest is to ever leave the sea, the sea will dry out and all the animals that live in the sea will die. So with their submarine and help from the sea animals, the scuba squad have to move the treasure chest to somewhere new and dangerous so the treasure hunters can never find it.