A man is stranded on a tiny ocean island. All that happens from then on is beautifully drawn and animated, but is quite metaphorical. It's all about the cycle of life, so try to read more into events than just what's on the surface. Hah, the surface, get it? Well, you will when you see the film.
There is absolutely no dialogue, just this simple story that somehow makes you feel stuff. The movements of the characters and animals are so fun and natural (maybe except a bat that was flying like a bird for some reason), the visuals are beautiful, it's a relaxing show.
It might put you off with the pacing, perhaps. I found myself looking at how much was remaining from the film several times, but most of the time I was entertained. I liked it.