Very nice, love the style.
As Adam said, would have liked to see more differences between each one, not that i can say much compared to mine. XD
I really like all of these. But I wish there was more evolution. As it is right now, it looks like the first one is crouching and then standing. I had to look for the differences when it should be more apparent.
I also like the implication of sand and ocean without being obvious.