While they are technically mutually exclusive, there are a lot of common threads between both aquatic exercises.
I started teaching swim lessons, and only about a year and half later started doing water aerobics. I would teach these group classes for the next 7 years. From the light intensity stretching based class "Move Your Joints, to the cardio or strength training centric water aerobics, to the advanced Water Boot Camp.
Why + Philosophy:
I loved teaching, and this gave me a chance to teach more. I would always interact with the people in the classes anyways, and this gave me more time with them. I found that I was good at it. I would make sure everyone had a good time, at least to the best of my ability.
Each person is different, and their needs from exercise are different too. I'd tried to personalize things as much as possible. Make sure people had the right weight, and were doing it all the right way.
I'd even give some people their own exercises if they weren't able to do what the group was doing.
How + Physics:
The structure I'd follow in the classes was pretty simple, and usually it didn't deviate. Although I don't like to do the same thing twice.
I'd start out with a warm up, usually consisting of things like running in place, running across the pool (something that is a lot harder than it sounds), jumping jacks, alternating knee raises, and my favorite: clapping.
It is astounding how something so simple can get you so much progress if done right. Keeping your wrists straight (something of a motto of mine), and doing it for a long enough period. You'd get a pretty good burn from that.
What + Psychology:
When I say water aerobics, people automatically assume it is an easy class. They think oh what are you doing ? Just walking through the water, dancing, and waving your hands? No.
It is a fitness class, and even some of the older clients would kick a young person's butt in the pool. You have to develop a deep strength to move through that water more easily. Since a lot of the exercises required movement, and even more so balance.
The people who took those classes were tough. At least the ones that tried!
While I moved on from teaching these classes, there is a still a part of me that misses them. I get guilt tripped any time I come back to say hi, but I can't help it. I want to be around the people who I grew up with.
I started teaching when I was only 19, and the only reason why I quit was because I was burning out from it.
It no longer gave me the feeling that swimming still does. That feeling of accomplishment I got when a student was able to make progress. It charged me up, and made all of the tough times better.
This is advice for people to level up their swimming, or perhaps get started in the first place. While you swim you should make sure you are doing so in a public facility with a lifeguard on duty for safety.