Open Water (2003)

Upon arrival at their hotel on an island holiday, it becomes clear that Daniel and Susan's relationship is under strain from their workaholic lifestyles, and they need a vacation even more than they realized. The next morning, the rested couple, certified scuba divers, board a local dive boat for an underwater tour of the reef. The boat is crowded with other vacationers, and due to a series of innocent miscommunications and a distracted crew, the couple is, after only 40 minutes or so underwater, accidentally left behind. What follows is the story of their ordeal: cold, alone and miles from land, the couple is adrift in shark-infested waters.