There's a hot spring under the ocean off the coast of Steep Ravine in Stinson Beach. It emerges for like 6h at a time - twice a month - for low tide.

People who were young and adventurous before there was an internet have been going for decades. They intentionally leave bad reviews on places like Maps and Yelp to try to dissuade new people from crowding it.

I feel like there’s a non-zero chance you’re getting downvoted because HN doesn’t understand sarcastic burner humor.