Three of us from Michigan dived Bonne Terre a few years ago. As mentioned, they have numbered dives or "trails" that you are required to dive in sequence. The first dive was a check out dive in a well lit room with a solid bottom at about 35 feet. After that, we followed our assigned divemaster, and were followed by another diver who really didn't pay much attention to what was going on. There were about 15 in our group, of widely varying skills. There are places where you might have 150' of water below you, and we had a couple of divers who lost control of their bouyancy and had to be caught and brought back to the main group. There were several swim throughs of maybe 20-30 feet, but as I recall they could be avoided if you were uncomfortable. The water was very clear, and about 52 degrees. We were comfortable, but several in our group got cold enough to cancel some of their dives.
I enjoyed the dives overall, but there were a couple of issues. First, if you dive DIN, make sure they have tanks available since you use their tanks after carrying your gear down a lot of steps. I had specified DIN tanks when I registered, but they didn't have any available when we arrived for our first dive.
Secondly, I thought our group was too large. We had a couple of divers who had problems with equipment, running low on air, or getting cold. There wasn't enough staff available to deal with everything that happened during our dives.
At the time the cost averaged out something like $80 per dive. I thought that was a little high, especially since you can't dive a lot of the really interesting rooms until you have done the first 6 dives. I enjoyed my dives, but I am not sure I would go back.