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Difficult
The best piece of evidence is the diving (not dabbling)behavior. I guess juvenile Ruddy Duck! Though I can't really tell you why. Maybe you remember what the tail looked like.

P. S.
Okay, I admit I could tell you why, I just didn't want to take the time. I thought there would be more opinions one way or another.

First, the overall plumage & bill coloration & patterning is consistent with juvenile Ruddy Duck.

Second, apparent proportions seem consistent with Ruddy Duck: big bill, big head, relatively small body.

The character that tipped me off is that faint sub-ocular dark line.

The timing of this photograph would indicate that this is a very young bird and even juvenile plumage is not well established, hence the difficult identification.