I think it was the uniqueness of this image that caught my attention. I don't think I've ever seen anything similar. I particularly like the eye-level position which grabs the viewers attention and focuses the eye straight onto the face.
I do find the space below the water wave a little distracting, there's nothing there apart from a partial reflection which I don't think is strong enough to contribute to the image. That said I do not know what you could have done to improve it either. The water line does lie on a third but somehow doesn't quite work.
The image to me tells a tale. I cannot help but think about why he is swimming away (or to) and where he is aiming to get. They say a good picture should tell a story so well done.
While the nose grabs the eye I do wonder if the old adage of focusing on the eyes would have served you better. After considering it further I think you have probably made the right choice in choosing the nose as your focal point. The colour and the fact that it 'leads the way' certainly provides impact.
On the whole an excellent image with great aperture control, colour rendition and impact. But more than anything else it tells a story and prompts questions from the viewer.
PS Can you supply some camera details?