During a recent visit to the Phinzy Swamp Education Center near Augusta, we spotted this snake from the boardwalk. I think it is is Northern Water Snake (Nerodia sipedon). This species is closely related to the Banded Watersnake (Nerodia fasciata), and hybrids do occur. Augusta is on the Fall Line where both species could occur. Hybrids also occur, further complicating the issue.
The photograph above shows the keeled scales which are characteristic of Nerodia. The round pupil of the eye can also be seen. Water snakes are often misidentified as the venomous Cottonmouth (Agkistrodon picivorus, also called Water Moccasin). However, the Cottonmouth has an elliptical pupil like a cat. A snake with a round pupil cannot be a Cottonmouth (or a Copperhead or a Rattlesnake). Water Snakes are ovoviviparous (their eggs hatch internally and the young are live-borne), and they may produce up to 50 young in a single litter.
We spotted this other snake some distance away and swimming away from us. The light was not good for a photograph, but I include this one, because I believe it to be a Cottonmouth. The triangular head, the very buoyant way of swimming, and the thick body are consistent with this view, but I would need a closer view to be certain. Maybe a better chance for a photograph will come along soon.
Water Snakes and Cottonmouths have many potential predators. Theses include Alligators, Snapping Turtles, Great Horned Owls, Red-shouldered Hawks, Herons, Cranes, and Egrets. Smaller individuals are taken by Loggerhead Shrikes and larger fish.