Wow, this is very informative. Thanks.
Do you call the bottom section of Morrison (
the second room) a Cave? Could one get Cave certified at Morrison, or do you need a more extensive system in which to demonstrate your skills?
As James said above, the large room is a cavern. Many of the fatalities occurred in the cavern section of Morrison. There is a section that goes deeper, and is considered a cave, but the opening is too small for a human to pass. It's also unstable, and there is a significant flow from the cave, so even if you were able to wedge yourself in, there's no guarantee you wouldn't cause a rubble collapse that could pin, or kill you, or both (first one, then the other). Before it was dynamited, the cave section was partially explored and mapped, but even then (I'm told) it was a harry transition into the cave section that challenged, and almost killed world-class cavers.
Different agencies have different requirements, but I think they all require you to dive three or four different systems to obtain your certification. I did four systems for my cert, and even though some of them were within walking distance of each other, they were all different, some significantly so.
Cavern is one of the best classes I've ever taken, and the price for what you get out of it is more than reasonable. If you are interested in taking cavern, be sure to talk with more than one instructor. Most of them are competent, but there are a variety of teaching styles. You can get a drill sergeant, a scientist, or a surfer-boy to teach these classes. Find someone (with a good reputation) who matches your learning style, and don't be afraid to ask other divers what they think of "instructor x" before pulling the trigger.
Above all, stay within your training. These springs have been here for millions of years, and will be here long after we're all dust. You have plenty of time to dive, and scores of places to do it. Get your training, find some good divers above your current level, and go diving with them. Many into cave, and full cave divers are happy to go for a cavern dive with someone who wants to learn.