You were probably a bit restricted because of the position of the trees. You can't very well cut down a tree to take a photograph, but it might have been better to step to the side a little, because that tree in the middle of the picture tends to obscure the view of the boat and rainbow. A different angle might work better too, to avoid the building in the background lining up with the top of the boat. I'd also remove that post thing - it isn't doing anything for the scene.
Having said that, you were lucky to get the picture at all - rainbows don't come along very often and when they do, they always add interest.
Edit to add: Was there a reason for the flag flying at half mast? If so, it would be something interesting to add to your description.