One of the best 'weird' movies ever

I thought this movie was a cool weird trip. It seemed like taking a trip through a depressed person's daydreams, but things weren't always totally bleak. Lots of twisty and unexpected turns, plus some hot naked girls here and there made for an interesting journey. I haven't figured out the back end of the movie, though: it seemed like shortly after he cooked and ate those clams on the beach, things started getting really weird. Were those maybe some sort of hallucinogenic clams??