Young Trot and the old captain, peg-legged Cap'n Bill, might seem like odd friends, but they are constant companions and Cap'n Bill taught her to love and appreciate the ocean. Trot was especially fascinated by the idea of mermaids and talked about them often with Cap'n Bill, who warned that no one who had met a mermaid had ever lived to tell the tale. One day while out sailing around, the pair is greeted by a beautiful mermaid who extends an invitation for them to come and visit their underwater kingdom and even become mermaids themselves for the adventure. Trot and Cap'n Bill meet a wonderful variety of characters along their underwater adventure -- eels and codfish and crabs, among others. After a marvelous and exciting time with the mermaids, the only mystery left is whether or not they will be the first to live to tell the tale of meeting the mermaids!