A rather standard horror/thriller flick. In fact it is so cliched that you could view it as a comedy rip-off off all the other similar movies, from Jaws to Moby Dick.
Basically a film crew is searching for a lost Indian tribe in the Amazonian rain forest, when their boat is commandeered by the baddie who wants to hunt down the real villian, a huge anaconda. This of course is the cue for the snake to kill off all the supporting actors, one at a time, until the final showdown. Guess who wins? :-)