I fully agree with the excellent reviews of the film by Blue-Grotto and comcockbot (the later obviously sat in the same screening as I), and their discription of the story is better than I would be able to deliver. So I will focus on the way the film appeared to me.
Nowadays hardly anyone uses the old academy standard aspect ratio of 1:1.33 anymore and I was a bit sceptic if this stands for an amateuric attempt or fake docu a la Blair Witch Project.
Far from it! The film consists of very controlled settings from the first to the last scene, there is nothing in it that doesn't advance the story or the mood of the film. At the same time it still manages to give you the feeling of an relaxed and slightly boring vacation time for a teenager. Minimal camera movements and long takes with no movement, always a tic longes as we are used to, gives you some uncomfortable moments and you don't know what to do with them, is there something more scary coming or is it just a joke to offset us? The film shifts between the trivial and harmless talks of the grownups and the more daring themes that the two protagonists discuss. The ghost story does appear to come and go. Again, is it just a joke of has it a deeper meaning? Find out for yourself.
Despite the fact the the scenes around the lake have not been technically enhanced, the lake looks not exciting but not mysterious either, the nature is beautiful as it is. The boy and the girl are both great actors and you always believe them in their struggles. The ending has been mentioned as to short to digest, yes, that is true, a bit more time would have been great. But all in all a beautiful film, very well planned and executed, congratulations!