I've only myself to blame.
When a film boasts that it has a group of tourists getting high on funny mushrooms, resulting in them being "attacked by ghostly creatures, never sure whether they are experiencing gruesome reality or startling hallucinations", the chances are it will contain tourists getting high on funny mushrooms, resulting in them being attacked by ghostly creatures, never sure whether they are experiencing gruesome reality or startling hallucinations.
And I am unlikely to really go for that.
So what we have is some young people, who start out alright, but become more repugnant as the film goes, running around a swamp, screaming, swearing, getting more and more muddy, while bodies and leering faces jump out at them in entirely predictable ways, while the camera zooms around in that style that has become quite trendy in recent years. Admittedly, a story that involves hallucinations is as good as any to be filmed in such a way, but that doesn't make it any less annoying.
The result is an incomprehensible mishmash; ugly (not so much because of gore, as there is surprisingly little, but the direction), dumb and, in the end, just dull. But I will give it one thing.
It's the first time I've ever seen a horror film with a talking cow.