There are a series of sea caves along Point Loma in San Diego that are fairly extensive. Back in the 1930's? there were tunnels carved from cave to cave. These cave are all formed in sandstone along joints. During prohibition there was a tunnel made from a cave up into a big house that is still there. The story is they used to smuggle in booze from Mexico. You can still see the wall in the back of the cave and cave Larry O'Brian said he saw the bricked up wall in the house many years ago. One of the carved tunnels currently has sconces carved in the wall as well as a pretty cool looking carved skull. I've heard stories of current day satinists using this tunnel for their nefarious purposes. Probably just some local kids having fun, we also joked that we needed to bring a virgin lamb with our caving gear of wetsuit, fins, and caving helmet. Also, one of the caves seals up at high tide. We used to swim into this cave as the tide was changing and the waves would reach the ceiling as they came into the cave. Quite sporting! You could feel it in your ears as the pressure increased. In fact there was a sand dig in the back of that cave that we dug on each time we went. Unfortunately, it would fill in between tides, we never did find the end to that passage. One story I heard was that a local monk used to swim into the cave and meditate through a full high tide. Anyway, the area is very colorful, and I thought you would like some those stories.
Tom