I was certified back around 1980 - in a flooded rock quarry in Ohio. Been on several more of those c-dives in quarries with friends. Always thought that was a rediculous way to introduce someone to open water - stick them in a rented wetsuit that doesn't fit right, and have them do their first dive in water that below about 5 feet deep is freezing cold, with vis somewhere between 0 and 10 feet.