Between Murphys, CA and Columbia, CA you’ll find the Natural Bridges Trail off Parrots Ferry Road. It’s a two-mile round trip hike that leads into a cavern fed by a creek.
The hike is slightly rocky but primarily a well-trekked dirt path with minimal incline. It’s so short and easy to hike that you’ll often find people carrying floaties from the trailhead all the way down to the cavern so that they can enjoy a float from one end of the cavern to the next.
Yes, there’s drinking. Yes, there is the occasional group of 3 or more adults. But I’ve never found it to be crowded or full of drunk, disorderly and/or rude people. It’s really a nice and relaxing spot to hangout and have some fun in the water.