Central South Carolina (USA). No indication of size:
According to the image name, it’s a deadly snak2.
Sorry, I got nothing 
It’s a horrible photo, but my guess is it’s a gopher snake.
Common water snake?
Looks like the Brown Snake, Storeria dekayi . The snake in the photo on Wikipedia is even striking a similar pose.
Good poster/OP combination there.
The markings make me think juvenile snake, which may make it harder to identify.
Juvenile garter snake, maybe?
It’s an eastern garter snake. Pics.
The OP photo doesn’t look at all like any of those garter snake photos. One thing all garter snakes seem to have are stripes running length-wise, and I don’t see any stripes on Earl’s photo.
Definitely NOT a copperhead; it does not have the classic rust-colored hour-glass markings and its head is not distinctly wider than the body.
I think Crotalus nailed it. Looks exactly like an eastern garter to me and he’s a bona fide herpetologist.
I read the title as Is this snake, and I came in with an answer and everything…
Garter snakes are amazingly variable. In some the stripes are barely visible and the checkered pattern is the most obvious feature, in others the stripes are very bold and the checkers can only be seen if the snake has just swallowed a frog or if it inhales to swell itself up. If you look through the array of pics I linked to, you will see a pretty wide range of bold versus less-obvious stripes.
The OP’s picture isn’t a real good one, but based on observations in the wild of hundreds of garter snakes, I am pretty certain that’s what it is.
Thanks, all.
Among the pics I linked to above was this one, which shows an eastern garter snake with barely visible stripes. They pretty much have just two elements to their dorsal pattern, the three stripes and the checkerboard, but the variations in those elements among the many I have seen is just amazing.
Are there any other snakes that have a similar style of checkerboarding or is that a good diagnostic for the species? I wasn’t aware of it before and it’s really cool looking. Amazing what nature can come up with, especially when contemplating the ‘why’.
The northern brown snake, mentioned by newme above, is also a variable species that also can have some checkerboard pattern. It also has stripes.
The eastern hognose snake may be even more variable than the garter snake, and it has a checkboard pattern in some phases.
Then there’s the eastern ribbon snake, which is in the garter snake’s genus, that has pattern variations similar to the garter snake.
And I’ll leave the question of why to others. 
ETA: While I appreciate lieu’s endorsement above, I am not a trained herpetologist, just a fairly knowledgeable layman. I have observed and collected reptiles and amphibians extensively in the eastern US, and worked for a few years milking snakes at a venom lab.
Concur with Crotalus – you can indeed see a cream stripe on the flank of the snake in Earl’s linked pic, albeit not sharply delineated (though how much of that is due to the 1990-era digital camera apparently used is debatable).
Scale is harder to ascertain, but said snake seems larger than I’d expect a DeKay’s snake to be; they’re typically described as “about the size of a pencil.”
And the snake looks too gracile to be a hognose – those guys tend to be robust widebodies.
Also, the area in question is – figuratively and literally – crawling with Eastern Garters; they’re quite common.
Duly noted, Crotalus and thanks for the links. Ooof, those hognose freak me out. There’s just something about thick snakes that doesn’t sit well with me.