Directed by Hans Horn, Open Water 2: Adrift (2006) stars Susan May Pratt, Richard Speight Jr. and Niklaus Lange. During a yacht trip, a group of friends jump into the ocean for a swim only to discover that nobody lowered the ladder needed to climb back aboard. Stranded in open water with no way to escape and panic slowly taking over, the group faces a desperate struggle for survival.

Från IMDB:
When a group of friends fail to lower the ladder of their boat, they find themselves stranded in the surrounding waters and struggle to survive.