In 1983 my first job (other than as an assistant instructor under my instructor) was as the program director for a health club. The owners had heard of "water aerobics/aquacize" but no one really had any info in what to do in the classes. So I went out to the indoor pool area with mostly senior citezens in a class. I tried a few things that didn't work (they really didn't like anything with their head underwater.LOL.
Well, the black belt in me decided to have them practice kicks and punches in the water. What I discovered was that with the resistance and buoyancy of the water, they were quickly developing some very solid basic kicking skills. Now, obviously they lacked quite a bit towards application, but for 70 year olds with no MA experience, there kicking base was impressive. Literaly, within a short period of time they were throwing decent kicks and even front kick-side kick combos off the same leg w/o setting their leg down.
Out of curiosity I had a few do these kicks out of the pool and they were firing them off with decent speed and power. Since then I have regularly included slow kick drills in the pool as a regular exercise in my warm month training routine. Also, I ahve always encouraged my students with access to a pool to do the same.