A tropical island, a World War II submarine, a brave dolphin, and 13-year-old twin sleuths. A non-stop adventure/mystery for children 8-12. It was just supposed to be a day at the beach, in the clear blue waters surrounding a small Bahamian island. Then everything changed. Sally was the first to see it - a dark shadow on the ocean floor. Carefully Sally, Jimmy, and their new friend Sandy swam towards the shape in order to get a better look and were startled by what they saw. What the heck was an old, World War II submarine doing in the waters of the Bahamas? That's just one of the questions that 13-year-old twins, Jimmy and Sally Brant need to answer as they find themselves in the middle of a dangerous, perhaps even life-threatening, mystery. Will they be able to solve the mystery, save the day and bring a nefarious kingpin to justice? And escape with their lives? A Modern Children’s Classic Adventure/Mystery Readers of The Sinister Submarine have compared it to Nancy Drew and Hardy Boys mystery adventure books. its non-stop action, with unexpected twists and turns, make it a clear favorite with both boys and girls.