It's a well-worn theme, a Nazi experiment goes wrong and BANG-O, everyone is in a heap of trouble.
The movie is "Blood Vessel" and I'd be remiss if I didn't say I immediately conjured up fond memories of the horror classic "Ghost Ship". Add that to any number of subsequent films where evil nazi experiments cause a big to-do and apparently you end up with "Blood Vessel".
This should be fun because it's also a period piece. The synopsis says the movie takes place in 1945 when so allied shipwreck survivors latch onto a vacant Nazi boat in hope of something to eat (perhaps some delicious Nazi burgers?). Well, as these things go, the new crew review ends up being snacks for some type of shapeshifters (they look more like vampire bats to me). I'm not sure how much shapeshifting they do, but this also brings to mind "The Thing" just a bit (IMDB clearly says these baddies are vampires, but if you watch the trailer, it says they are shapeshifters)
Wrapping it up, the boat setting is always awesome because it seriously cuts down on the possibility of escape and adds a claustrophobic element to the story. You can catch "Blood Vessel" streaming exclusively on Shudder right now).