@red river hog Bulky proportions (especially the heavy back half of the bird), bill shape, bold color of eyering, white on wings, and leg color all point to Domestic Mallard. I've looked into it and I can't find any domestic breeds of Laysan Teal that look like this, I think this is just a Domestic Mallard.
@birdsandbats That's my wondering after a bunch of searching around. It doesn't look quite right for anything in particular, including any variant Mallard i can find.
Edit: Hybrid with Laysan Teal doesn't match either, nor hybrid with Hawaiian Duck. Might well be a funky Mallard...