It isn't the best movie ever, but it's entertaining enough, and considering the limited setting and cast (all movie long we are on the same boat with the same three people) it's quite an achievement that they made it thrilling until the very end. I especially liked it, that up until the last say 20 minutes you keep guessing who speaks the truth and who is the villain. Ella-Rae Smith plays her bewilderment and deadly fear very well, Matthew Daddario as handsome and charming Ben makes it totally believable that young Jess falls for him, and Jessica Alexander is equally convincing as the relentless vengeful Lexie.
I do have a few minor reservations. The sad personal history of Jess keeps popping up, but doesn't add anything to the story. And the last scene somehow gave the impression that the makers considered someone as a hero and worth to be saved, who in my opinion was, in spite of understandable motives, disproportionally violent, even murderous. A bit of a questionable moral, I would say. But for the rest: a nice and entertaining thriller.