A harmless Gartersnake resting near the river (Thamnophis sp.).
Looks like a Mountain gartersnake (Thamnophis elegans elegans), a subspecies of Western Terrestrial Garter Snake (Thamnophis elegans).
If you can confirm the identification of this Garter snake, please post a comment or email me.
Photo taken during a 3-day trek on the Pine Ridge trail to the Sykes Hot Springs in the Vantana Wilderness, near Big Sur (California)