What did I learn? Hmmm
I learned how to use a double hose regulator (my newest very cool toy, a completely rebuilt 1964 DA Aquamaster) I learned how to clear the mouthpiece when it fills with water, how to position your body for maximum breathing efficiency, I saw how close I was able to stick my mask right up to fish resting on rocks and watch them - bubbles come out from behind you so they don't spook the fish. I found out what it feels like when your tank runs low on air (expected- calculated depth & time) then pulled the J valve and got full air back. I knew then it was time to make my way up and go back to the beach.
All this was done in a wetsuit in 53 degree water diving minimalist with no BC, no SPG, no computer, just a tank on a plate, my new baby, a bottom timer, and a compass.