If I could rate the killing-scenes alone, I would probably give an 8, they are really awesome, with an original and inventive use of constantly the same weapon. Unfortunately these scenes had to be patched together by some story, and here this movie fails utterly, the story is as flimsy as cardboard and full of improbabilities. They made it into a who-dunnit (which at least makes you sit the whole thing out), but if you expect a serious motivation from the at last revealed killer you'll be disappointed: the script provides him with a lame self-pitying whine that hardly explains his totally disproportional killing-spree (but I guess we can't expect a psychopath to be rational anyway!).
Another problem: the guys and girls are all equally unsympathetic, all wise-cracking party-animals, loudmouthed and wannabe cool (the guys) and lascivious (the girls), so you couldn't care less if any of them got to be killed anyway. The acting is over-all below par (even from nowadays famous James McAvoy, how he got involved is a mystery in itself!) and most of the actors talk English with heavy accents (apparently this is a German movie but for some reason shot in Prague). And for a movie about wild and hormone-driven teens that constantly talk about sex and are illegally partying in a desolated pool it's surprisingly prudish, with most girls wearing a one-pieced bathing-suit and all the guys colossal XXL-sized trunks.
In conclusion: just watchable for the awesome killings!
