An interesting choice of subject but I think that you should either crop it closer to the buoy or zoom in closer. Your main subject is literally swimming in a vast water that is largely uninteresting to look at. Now yes, that does call our attention instantly and directly to the colors & shape of the buoy, but you could do that just as effectively if you presented the viewer with a closer look at the main subject. Bring the buoy to us, make it dominate the scene and strengthen the visual impact by zooming in to make the buoy occupy 70% or more of the composition. Those bold red and the white hues would visually 'pop' off of the flat grey water if it made up 70% of the compositon. A square crop could even more of a dynamic to the visual because it tightens the focus on the subject even more AND it can be a subtle addition of just another shape juxtapositioned with the round shape of the bouy. Good idea and holds promise but the presentation needs improvement.
I'm not really sure why I like it but I do...sorry I don't have anything to say to help improve the photo...but, I don't see anything wrong either. Good luck to you...683 photos in this challenge! It's gonna be tough for all of us...I'll give it a 7.
I think a little bit of contrast would help you out here, just to make the buoy pop out a bit more. but maybe this is what you were after ;) composition could be a bit out of the middle, reflections in the water are nice