I was in aqua therapy for a couple of months, the PT will usually tailor make the session depending on many variables (type of injury, severity, age, fitness level etc, etc.) I’ll go through a typical session of mine (I was 1 ½ months post-op from a 3 level fusion when I started).
I started walking forward about 5 minutes, then backwards 3 minutes, then I side stepped the length of the pool from left to right about 5 times (about 5 steps each way, it was a small pool), I would then do about 25 squats, then I would sit down and do leg lifts (I started doing 10 lifts per leg (no weights) and graduated to 30 lifts per leg (with four pound ankle weights) after a couple of months).
Also while sitting, they gave me a mini kick board that I would place in front of me. I would place both hands on top of it; I would then push it down into the water and move it to the left and then to the right all while keeping it submerged (don’t turn your body too far to the side if you have had surgery!!!). This helps strengthen your abdominal muscles. It helps to wear ankle weights while doing this one as you have a tendency to rise out of the water while pushing the foam kick board down into the water.
They also had a current machine, I would walk forward into the current and then walk backwards away from the current, and this was great and also helped fire the core muscle group.
But, in closing, like you said, just getting into the water is relaxing. And for the finale, what I looked forward to the most was at the end of the session, they would have me put a floatation belt around my waist and I would rest my legs on another belt and I would float on my back for about ten minutes (usually more if I could get away with it), talk about relaxing…oooohhhhhhhh yeeeeeessss! I still do this as I talked the insurance company into buying me a couple of these belts and I have been in our pool and hot tub almost every night for the past eight months since my surgery. I usually spend at least an hour a night sometimes 2.
I hope this helps, good luck, and like any PT would tell you, start out slow, and if something causes you any pain, STOP!