Any clue what kind of duck this is? My first thought is that it's a juvenile mallard but I couldn't find a photo of one that looked anything like this, especially that white chest. Maybe it's some kind of mutant or hybrid or ?
I saw a young one that was accompanied by a male and female mallard. I think forum member @Alan also has a few photographs of these types of ducks, too. Nice photo, Dave!
Just a common mallard hybrid -- the females are very promiscuous and will favor any male with a green head; with all the inbreeding and close crosses, the coloration of males is highly variable. The tell-tale is the curled hind feathers.