The Boy and the Magical Shell

Thirteen-year-old Justin has about had it with his sister and her friend. When he goes to the beach in his little harbor town to blow off some steam, he comes across a shell necklace. The necklace ends up belonging to an underwater world full of mermaids and magic! When a British dolphin mistakes him for a merboy (because of his necklace) and takes him to the mermaid colony, a mergirl, Cora, befriends him and tries to get him back home before he is trapped in this new underwater world forever!