On the Reef (Andrew Lost #7);

Andrew, Judy, and Thudd are out of the whale, but not out of trouble, when the Water Bug gets caught on the Great Barrier Reef! This is the third in a four-book set that will take the kids on a tour of undersea phenomena—from the Great Barrier Reef to the Mariana Trench to the inside of a whale—as they try to find their way home.