I am going to guess that it is a baby rat snake based on doing some more searching. Confirmation of my guess would be greatly appreciated. Here is another photo.

Thanks!

Baby ratsnake. Completely harmless.
Depending where on coastal SC you live, that snake would have grown up to be striped with a dark green or yellowish background.

Thanks. We see the adults often with a yellowish background.

Glad to know it is one of them.

These are really common in the lowcountry, judging by my experience with them. They are very good tree climbers, by the way! It's a little unnerving seeing one 'scale' a loblolly pine or a big live oak.