In the movie, American couple Susan Watkins and Daniel Kintner are accidentally abandoned by their dive group off the Great Barrier Reef. In real life, American couple Thomas and Eileen Lonergan
disappeared after they were accidentally left by their dive boat in the Coral Sea. The dialog, the scenarios with shark bites and jellyfish stings and small fish feeding on wounds ... that's all invented. But the basis for the story? It's real. And really terrifying.