We had one that looked similar - looks like what is known as a Brown Water Snake.
The brown watersnake is a large snake with dark brown, squarish blotches running down the center of its lighter brown back. This species has alternating rows of square blotches that run along its sides, thus resulting in somewhat of a checkerboard appearance. The belly coloration is variable but is usually a mottled brown color. The eyes and nostrils are situated near the top of the head making it easier for this snake to breath and see at the water’s surface. These snakes are commonly found during the daytime basking on tree branches overhanging the water, into which they escape if disturbed. Unfortunately, this escape strategy may land a brown watersnake into the boat of an unsuspecting fisherman.
Feeding/Diet: The brown watersnake feeds primarily on catfish and is sometimes found with the spines of catfish sticking out its body walls. Surprisingly, the spines eventually fall out and the snakes seem to recover from these “painful” meals.
Habitat/Range: Brown watersnakes are primarily found in rivers or large streams in the Coastal Plain of North Carolina; however, they do extend into the Piedmont along large river systems.
Reproduction: This species breeds from April to May, and females give birth to 15–50 young during late summer or early fall.
Miscellaneous: Like most other watersnakes, brown watersnakes are often mistakenly identified as cottonmouths and killed. When captured, these snakes, like other watersnakes, will bite repeatedly and emit a nasty smelling musk from their anal glands. Female brown watersnakes grow longer and much heavier than males. Although nonvenomous, the bite of a large, female brown watersnake can be quite painful.
