Megan and Marcus can't wait for the summer holidays to begin at Bexhill-on-Sea, where their own incredible beach hut, Parry, doubles as a high-powered rocket ship. Before long, they are heading for Australia on a thrilling mission. As secret agents, they must confront a dangerous gang to try and save a beautiful beach from certain environmental ruin. When they spot a massive crocodile mysteriously devouring all the famous white soft sand on Whitehaven Beach, things start to go seriously wrong. Marcus sees Megan being swallowed by the reptile and does not hesitate to plan a daring rescue...