Question: After the tour guide takes the bad head count when they all get on the boat, you can see him counting them all again. Why didn't he notice right then that 2 people were missing? Also, the diving company was missing 2 scuba tanks and they didn't notice?
Answer: He counted wrong because the man that begged to go back in and the other person accompanied him in the water were already counted for before going back down last minute so when he saw two people coming back up he tallied 20 people.
Question: Where is the film set and where can I read up about the true story?
Answer: The film was inspired by an incident at St Crispin's Reef, a dive site on the Great Barrier Reef in 1998, when Tom and Eileen Lonergan was left behind by their diving boat after an error was made during the headcount. They were never seen again. More information can be found at http://outside.away.com/outside/features/200310/200310_mysteries_2.html.
Answer: The whole idea with the movie was the bad count. Nobody knows why he counted wrong.
Mortug