To meg and other concerned divers:
As for diving and fear of water, maybe you should check out your local aquatics centre for a private lesson in deep water activities. I know we offter those at the pool I work at. We do things like jumping off the edge, off the diving board, going down a pole as far as you can go, etc. It might be something you should check out if you want to try the SCUBA experience.
You may also be able to take an intro to SCUBA course for an afternoon (around 40$ Canadian/30$ US I'm guessing with the conversion rate) just to get more practice.
As for the ears, if you can fly to camp and have no troubles with pressures in your ears, you should be fine. They shouldn't stay popped or unpopped. Just take it slowly and remember that your instructor is there to help you if anything doesn't feel right. Even if you take the whole time just to get to the bottom of the tank it will be worth it!
You can do it! The hardest part of overcoming a fear is trying one thing beyond what you have done before. If you can move just one step ahead, you have success! If last time you made it to the platform, then maybe next time you can make it down a few steps of the ladder. And hey, if you're going down the ladder, let your excitement guide you and go all the way
All the best wishes. I hope you will have a great UAT experience! If you set your heart out to do something, then do it; never let fear get in your way!