Jack and Annie are ready for their next fantasy adventure in the bestselling middle-grade series-the Magic Tree House! IT'S SINK OR SWIM for Jack and Annie when the Magic Tree House whisks them off to the middle of the ocean. Luckily, they find a mini-submarine on a coral reef. Unluckily, they are about to meet a giant octopus and one very hungry shark. Will the dolphins save the day? Or are Jack and Annie doomed to be dinner? Visit the Magic Tree House website! MagicTreeHouse.com From the Trade Paperback edition.