That got me thinking about last summer in Mexico, where we got to swim in underground caves called sometimes.
This is me swinging into an open cenote:
Sean doing a happy underwater dance:
And there was another one, inside a cave, where we snorkeled:
Another beautiful thing is to see a ray of sunlight coming through a hole in the top of the cave, and falling all the way through the water to the bottom.
Some underground caves are connected to each other and you can even scuba dive from one to another. Really really cool, so if you are in Mexico definitely try it!