This waterlogged adaptation of an obscure Grand Guignol stage play finds a hapless couple (Dermot Walsh and Hazel Court) convinced that their newly-acquired yacht is haunted by mysterious and deadly forces. After numerous fatalities, the couple eventually hires a paranormal investigator (John Robinson), who uncovers the yacht's bloody history and determines that the craft is occupied by the vengeful ghosts of the former owner's wife and her lover, who were murdered and subsequently entombed somewhere aboard. Writer-producer-director Vernon Sewell -- who filmed most of the scenes aboard his own private yacht -- executes a few interesting paranormal twists on the Old Dark House scenario, and he would revisit the seagoing thriller theme (on the same boat) somewhat less successfully with Terror Ship two years later.