Hi Kmun, hope you have fun swimming with your DD. I can only speak from experience, but I am now on the 2nd course with water babies and finally my 7 mo DD loves it (she did spend about 3 lessons screaming her head off, but like one of the other posters above, we perservered and she now loves it again).
Where we go there is a strict 'no buggies' rule both poolside and in the changing rooms. To get round this I just take DD in her car seat and make sure I have her favourite toy so that when she is dried and changed after swimming she is kept happy whilst I quickly change out of my wet things.
I was also concerned about how to get in and out of the pool with DD. For the first few lessons the instructor took DD from me and then handed her to me when I was in the water. Now I lay her on the side of the pool, feet facing the water & get in the pool next to her. Same for when I get out. One thing the instructor said is to never hold the baby whilst getting in or out using the normal swimming pool type steps. She said that if there was no other option, then ask a stranger to help rather than do that.
As far as I know, no bouyancy aids are needed. But what I do use is a little baby wetsuit for my DD. As I said earlier, she did get very upset for a few lessons, so I thought one of the reasons might be that she was getting chilly. The wetsuit certainly seems to have helped.
Where we go they insist on a 'double nappy' system -- disposable swim nappy under a resusable swim nappy to avoid any spillages (apparently the pool would have to close for 18 hours if there were any accidents!).
The only other thing I would say is gone are the days where I used to shower, dry my hair, do my make-up, etc after swimming! Now it is just get DD sorted and comfortable & get out of my wet stuff and into a tracksuit as quickly as possible!
Enjoy it!!