When Chad escapes with Danielle through a secret passageway, he kicks open a door to get outside but when the door opens you clearly see another room. The movie then cuts to the supposed other side of the door which is outside.
When Chad and Danielle are on the boat after their swim in the harbor, Chad's clothes are perfectly dry while hers are hung on a line down below to dry out while she has a towel wrapped around her. However, her hair has the look as if it has been blown dry. It's doubtful Alex would have carried a blow dryer on his boat.
When Chad and Danielle are on the boat after their swim in the harbor, Chad's clothes are completely dry as well as his hair which looks as if it has just been styled. Danielle's clothes are hanging on a line in the bottom of the boat to dry out, but, her hair has just been blown dry without a blow dryer on the boat. Alex would not have kept one on the boat since Danielle had never been to the island before.