for a beach/sky picture, there's just too much middle ground. Also, all of your movement is happenning in that middle ground, and that will draw my eye every time.
I love this shot, the composition and cropping but that is about all I love. The colors seem off for some reason to me and the lack of focus overall is very distracting in the end. If you handheld the camera for this shot, try a tripod or monopod (I think that's what they call it) and see if that helps with the focus aspect. As is a 3
In my opinion the contrast between sky and beach isn't sufficiently strong to meet the challenge. You could probably make this more intense in photoshop.