Um, like in every slasher movie since the 1970s Texas Chainsaw Massacre?
Before I watched The Watermen, I read some pretty terrible reviews on it (and then watched it anyway). Okay, it's no masterpiece, but its overall flaw is its lack of originality. It's about a group of teenagers who go on a boat and get picked off by a gang of mumbling nasty fishermen on another boat who want to turn them into fishfood. Basically, it's Texas Chainsaw on water.
It's very low budget. Therefore don't expect too much gore and any nudity is pretty fleeting.
After watching the film I couldn't really think of anything that bad about it, apart from I've seen it all before - not just once, but dozens of times. It's basically a carbon copy of every slasher film that's gone before it.
Bottom line: there's nothing wrong with Watermen, but there's nothing original enough to make it right.