Borrowing heavily from both "The Lord of the Flies" and Francis Ford Coppola's "Apocalypse Now" (itself based on Joseph Conrad's "Heart of Darkness"), the story does have a fair amount of built-in intrigue due quite simply to the time-tested plots.
While it thumped along, I had plenty of time to ponder the other and better movies that it reminded me of: The Mosquito Coast (1986), The Deer Hunter (1978), and Apocalypse Now (1979), as well as William Golding's novel Lord of the Flies.
Here, DiCaprio swallows caterpillars, totes an AK-47, slays a shark, gets high and mistakes himself for Martin Sheen in "Apocalypse Now" or is that Charlie Sheen in "Platoon"?
The film indexes Apocalypse Now, and The Deer Hunter, as well as The Blue Lagoon and Ursula Andress's sexy bikini scene from Dr. No, with a little bit of The Lord of the Flies thrown in for good measure.
("Primal" being a relative term here: mostly he skulks around the brush wearing a headband, in one of the movies many blasphemous allusions to Apocalypse Now .)
When the film finally stops boring us with an hour long onslaught of pretty trees, clear water, and tanned bodies, it just becomes this really weird combination of Lord of the Flies and the last 30 minutes of Apocalypse Now.