I love diving or ambient pressure diving, you become directly exposed to the pressure of the surrounding water, it is thrilling!
I've never done that but I have always wanted to learn! 
My favorite is scuba diving, where you use the self contained breathing apparatus to go even deeper.
That's what I always wanted to do on the great barrier reef. I bet it would be beautiful.
The technology of underwater diving actually started with stone weights tied to a person to make a fast decent. One of my favorite things to do.