Interesting place! They process up to 50 divers an hour and so the process is very regimented. I'm not sure how it works in general, but since you must dive with a buddy, I made a "reservation" with an instructor to be my buddy (20 Euros for the dive, 30 for the instructor!). You are supposed to arrive one hour before your dive to sign up. Dives start on the hour. At 15 minutes before the hour they ring a bell signaling that the next group can head to the locker room. You
change into your swim suit---no wetsuit needed as the water is 33 Celsius---91 Fahrenheit. You may bring your own reg (but NOT DIN) full foot fins, mask, etc., but no BCD, tanks, or weights---they provide all (tanks are 12 liter, 232 bar, steel, thus no weights needed). On the hour you grab some of your gear and snorkel/free dive for 10-15 minutes. Then it's time to scuba. You get your BCD and tank and go diving. My buddy/instructor was a woman in her late 20s or so.
She asked what I wanted to do. I said, "well, I have problems equalizing but I would like to go down, get comfortable, and then go down to the bottom." And she said "so you have come to the deepest pool in the world and want to go to the bottom?" (I guess she had heard that one before!) And I said "yes!-- Let's get to the bottom, stay for a bit, come back up and play in the 30 foot range." So off we went. In a few minutes, there we were at 33 meters*. It was a bit crowded going down with enough divers below us to make the bubbles annoying. We stayed at the bottom for less than a minute. On the way up she stopped me at around 60 feet---I assume we were doing a deep stop. After a few minutes we were on our way up. At around 30 feet They have a couple of swim throughs with air pockets, so we went in both of them, chatted for a bit and then were on our way for some playing/prolonged safety stops. We finished the dive at 39 minutes. She asked, "so how was it?" (Her tone was a bit apologetic about only 39 minutes.) I said "it was fun!" She answered "yes! But everyday?" I understood what she meant. It was one of those things that was worth doing but I am not in a hurry to do it again.
(*Subsequently, after checking my computer and doing some calculations [the computer was set for salt water and was reading in feet] I e-mailed them and said that by my computer/calculations their pool was 35 meters/115 feet deep. Their reply indicated that I was correct. Maybe Nemo 33 sounds better than Nemo 35!)