Robbie, I understand what you mean, but remember, we're not painters, we're photographers, which means that we are limited by our physical environment and/or by the technical limitations of our equipment.
And in this case, it was both : I couldn't place the subject more to the right, because then I would reveal an ugly and disturbing boat (and some other clutter) to the left of the camera. A possible solution would have been to shoot from (much) further away with a tele, which would give the opportunity to compress the visual information. But, a tele is something I don't (yet) have so this wasn't possible for me.
In short: I think I chose the best possible composition that I could, given the situation and the lens I was using. :)
Also, I don't really consider the right part of the image as "useless", I kinda like it. I think it emphasizes the sense of space and solitude.
Excellent find. For my own taste I'd have tried to put the main subject somewhere else but not in the middle of the frame. More of this fence on the left and less empty sea on the right. But I guess you had no other option.