Actress Emma Caulfield was originally cast in the movie as Lauren, the strongest swimmer of the group. But upon arrival at the shooting location, it quickly became apparent that Caulfield was terrified of being in the water and was replaced.
The original script for the film was simply called Adrift, and was based on a short story by author Koji Suzuki, best known for writing the novel Ring which then became the film Ringu (1998), a Japanese horror classic. The script had already been written before the release, and success, of Open Water (2003). It initially had no connection to it. When the script was finally picked up for production, it was retitled Open Water 2: Adrift in certain countries (including the United States) to capitalize on its success.
Promotional posters claim the film is based on actual events. This is false. The actual script is an adaptation of Koji Suzuki's short story Adrift, a piece of fiction. The marketing tactic comes from the success of Open Water (2003), which was actually based on a true story.
The song in the opening (seeing the characters driving to the port) is called "Godspeed" while the yacht also has the name "GODSPEED" on it.
To prepare for the movie, Susan May Pratt went to the tanning salon and worked out to prepare for a lot of treading water.