I've re-uploaded this (deleted the old one)
The sun was just outside the top left corner of the frame, so the light refracted through the water had red tint to the naked eye.
(f4.8, 1/3000s ISO160)
I think in future I'm going to upload to flickr directly and then import to this gallery from the url, as I'm not sure my colours are always as envisaged when i upload directly here.