Now here's a shot I can relate to. I love my fisheye (very simiilar, at 16mm, to yours) and know how hard they are to use effectively. I know nothing about skate boarding, though... Here, I think there's a bit too much foreground, which tends to de-emphasize the figure. Maybe, if you have a good relationship with the skate boarder, try to get a little closer to him at some critical moment of arrested motion? I guess he'd have to be pretty skillful too. You also have to beware of over-bright skies when you're shooting into the light as you are here. Of course if you have the light behind you your shadow is going to be in the picture for sure! Fisheyes are hard!! It's all very well to suggest fill-in flash, but there's no flash unit going to be able to give you the angular coverage you would need.
I like the angle of this alot. I really wish there was a flash that was there to light up the skaters front side more. Perhaps then you could have closed down to ge those nifty clouds exposed right too.