It could be a mix of a bunch of things and it looks like a mixed breed mallard x domestic duck took me. What we do know is that at some point back in this ducks ancestry the genetics of a wild Mallard were mixed in.
Cornell Lab has a good article:Confusing Domestic Duckshttp://www.birds.cornell.edu/crows/domducks.htm
Cornell Labs wrote:
It’s a domestic duck.
This is probably the most common answer to most beginning birder’s duck problems. Domestic duck breeds are not illustrated in most field guides, and the older guides did not mention this problem at all. When people go out looking for wild birds they seem to forget that domestic breeds exist. First rule of thumb: If your weird duck is found at a park, walking around on the grass or coming near people, it is probably a domestic duck. But, these domestic monsters do get mixed up in flocks of wild birds, too, so how do you spot them? Second rule of thumb: If your duck has large patches of white where you didn’t expect it, think domestic duck. People seem to love to breed white or partially white domestic animals, presumably because such mutations don’t do well in the wild and consequently are rare. Such mutations do turn up in the wild, though, and we’ll discuss them later, but for now, if you see big patches of white, think domestic duck.