A team of 6 friends head out on a journey together to make a documentary about Epecuén (a tourist village in Carhué, Argentina that - in 1985 - was flooded and abandoned) and is sometimes described as the real life Atlantis. It was underwater for almost 25 years. Since 2009 the water level has been decreasing and the ruins of the former lakeside resort, has become a tourist designation. The friends take a wrong turn, no pun intended, considering the turn was right, but you know what I'm getting at here, in the genre every turn is in the end, a wrong turn. Along the way they bump into some sketchy and rather interesting characters. When their van breaks down, and they have to split up, shit happens and the race against the clock begins.
For me to feel any type of way for a character you're gonna need to give me some depth, if I don't fall in love with this character somehow - either by wanting to be with them or be them - chances are slim that I will actually care if they live or die. I don't know these characters, I have no clue what they're about and couldn't care less what happens to them. What the Waters Left Behind reminds me of "Texas Chainsaw" and The Hills Have Eyes, with a dash of Wrong Turn and a sprinkle of Wolf Creek. I understand drawing inspiration from movies - hell even I do that when writing - but in all honesty, this just seems like an updated Spanish version of the ones mentioned above and therefore fails on deliverance, due to its lack of originality. Didn't realize how much I did not need this, until I sat down to watch it. Now I know. And of course, our taste in this beloved genre of ours will always be different, some may absolutely love it and some not so much; that's the way it's supposed to be. There are films worse than this, so happy viewing and whatnot.
Substitute nuclear fallout with receding flood water, and Carhué, Argentina for San Diego, California, and you've more or less got What the Waters Left Behind; a less compelling, messier version of Alexandre Aja's 2006 remake of The Hills Have Eyes. Given the Onetti Brothers penchant for homage (their other notable films are the giallo inspired Sono Profondo and Francesca, the later of which was a favorite of this site), it's no surprise What the Waters Left Behind is what it is, but unlike the aforementioned giallo tributes, this one unfortunately left us feeling a little bit dry.
Even so, I was never bored. At the very least, What the Waters Left Behind was a visually stimulating, well shot horror film. The last two aspects in particular, are areas that have never been a problem for the Onetti brothers. Colors are appropriately drab when necessary (the excursion above ground for instance), and are allowed to pop during the film's more exhilarating and violent moments, giving the presentation properties of hyperrealism. I liked it, but it's definitely an acquired taste, especially for a film like this (some may prefer a more consistent tone).
Speaking of violent moments, gorehounds will find a lot to satisfy their twisted appetites. Highlights include limb severings, cannibalism, gouging, stabbings, and some good old fashion bludgeoning; and the best part is that nearly all of it comes by way of some very convincing practical effects work. Given the relatively low budget the film has to operate within, it's both impressive and absolutely welcome. One of the first things to suffer with films financed at this level, are the effects work - typically eschewing (by necessity) practical, for stock CG.
I say, if you were already interested in watching "Waters", then go in understanding that you aren't going to see anything that hasn't already been done with these type of films in the past, and in some cases, done better. See it, if for no reason than to kill a couple hours with a visually striking gore-romp. Like Vicky said, you can do worse.