we did a dive to 110 ffw in a large quarry, temp around 55-60, cant remember.
Our instructor killed the idea of opening locks as it is not a real world application. Instead, he had us (me, my buddy and a diver we never met before) check each others depth, PSI remaining and time every 4 minutes during the dive and record this on a slate.
As easy as it seemed, I had a helluva time getting any information from the third diver after we passed 80' until we were back around 50' on the ascent.
I know it sounds easy, but it was a challenge staying on task the first time that deep. Maybe I will take a lock with me next time and see what that is like.