Northern Watersnake (Nerodia sipedon) 95% confidence.
Genus Nerodia 100.0000% confidence.

Unlike a lot of the pictures I see, I couldn't blame a "non-snake person" for thinking it was a Copperhead or even a young Cottonmouth. But even then, comparing a few pictures should make it obvious.
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What goes up must come down...unless it exceeds escape velocity.