The transition from dive bomb to gliding can be very tricky... I tend to pull up too hard. I think I burned 1.5 hours trying to complete Advanced AR 2 & 4. I was determined to get them completed.
The easiest trick for the water one is to just let go (at first) and don't pull up from a dive bomb. After a couple seconds, then start to pull up and you'll get it.
I'm sort of upset with the AR training in that I completed it (as well as several other difficult achievements) and Windows Live LOST my achievements. The Steam achievements are there, but not the Windows Live achievements.
(And due to the nature of the game, I can't just play a New Game+, I have to restart from scratch, and several of those achievements were near the very end of the game).