Hi David,
This is a lovely peaceful image and I am enjoying the clean, high-key treatment.
There are two things that I would like to see fixed up in this photo... the first is the rubbish that is floating in the foreground of the picture, particularly in the lower right-hand corner. It only takes a couple of minutes to go through this image with the Spot Healing Brush tool to clean it up; as soon as you do this you will discover that your eyes will linger on the buildings and boats rather than on the weed in the water.
The only other thing that I would like to see is just a hint of detail in the sky. If you captured this photo using RAW then chances are you can go back and pull in some detail into the sky.
Cheers, Anthony