'De Zee Die Denkt' ('The Sea That Thinks') is a weird, thoughtprovoking film about itself and about a script writer struggling with the question of what the 'I', the self, really is. Like a Zen koan, the film tries to unsettle the viewer's expectations and thinking patterns. It abounds in visual puns and clever trickery, Escher-like impossibilities and meta-play.
The story, or really the discussion, draws heavily on Buddhist philosophy, which asserts that all reality, including the self, is illusory, and it is people clinging to their ego that causes their suffering. The script writer in the film tries to get his mind around this idea, but he gets stuck in a kind of Cartesian paradox: for all his lofty ideas, there is still an 'I' who is having them.
The whole idea that we are an 'I', a somebody, is an illusion. I think.
Ultimately, the film doesn't really get beyond this paradox. (In the context, you might say it doesn't succeed in transcending it.)
Its greatest merit is in having found a playful form for some difficult, abstract ideas. And it still offers much food for thought (leaving aside the problem of the 'I' who's doing the thinking).