Come to think of it, I think the one who stole your bait is also a watersnake, maybe juvenile, not a corn. I don't think it's a water moccasin = cottonmouth as they are only found in the southern states and you're in MA, right? Did you get a good shot of its eyes? Are they slitted or round?
In any case - steering clear of any of them would be my POA as well.
BTW - it's a pretty awesome photo, the snake going for the fish bait.