Puck, the fairy pony, and Holly are visiting the Pony Queen when a powerful magic necklace-- which grants its wearer whatever they wish for-- is stolen from her Summer Palace. Puck and Holly's search for the thief leads them into the underwater world of the river ponies, an enchanting place of coral houses, clear waters... and dangerous sea creatures. When their adventures finally bring them to the culprit, they find themselves face-to-face with a...