Jamie and Tom are off for a spot of snorkelling in Dinosaur Cove, and they've even brought a bodyboard for Wanna! As the boys dive under the water Wanna drifts out to sea - how are they ever going to save him? Especially when a huge plesiosaur is lurking beneath the waves with his terrible snapping jaws! Perhaps a passing school of dolphin-like ichthyosaurs may just be able to help . . .