Triangle

Triangle is a 2009 British psychological horror thriller film written and directed by Christopher Smith, and starring Melissa George and Michael Dorman. The film was released in the United Kingdom on 16 October 2009. George plays a single mother who goes on a boating trip with several friends. When they are forced to abandon their ship, they board a derelict ocean liner, where they become convinced that someone is stalking them.

source: https://en.wikipedia.org/wiki/Triangle(2009_British_film)