A charter vessel captain buys a secondhand boat; it turns out to be haunted. Trashy maritime horror with a solid cast doing their best with scrappy material. There are some effective moments, but the lack of actual story is problematic, as is the way the film gives up in its third act.
Part 3 is a prequel, offering backstory on Elise, and her team-up with Specs and Tucker, plus another demonic yarn. Lots of jump scares, handled well enough if you like this sort of thing, with series screenwriter/actor Whannell now elevated to director.