Thamnophis saurita sackenii, the Peninsula ribbon snake;
Lake county, Florida (19 January 2017).
Peninsula ribbon snakes are closely related to the more commonly recognized garter snakes. Ribbons tend to be a bit thinner and, well, ribbon-like. I tend to find them very close to bodies of freshwater. Note the white line in front of the eye; garters lack such a prominently bold white line.