Are you doing any of the above? If yes and you are a senior, you are not doing your body any favors. You need instead the full cushioning effect of the water to protect a body that is now easily subject to injury.
However, if you are using a swimming stroke that cushions your body in full, as shown to the left, you are on the right track as a senior and have many wonderful swimming years ahead of you. This is my exercise as a senior and I use everything but those competitive strokes nowadays.
When a person of any age or sex is swimming in our condo pool, usually nine out of ten of them are swimming the crawl. I used to be one of them. However, some years and injuries ago I realized I was not helping my body by swimming this one stroke. The primary reason I was hurting my body was that I was lifting it out of the cushioning effect of the water every time my arms did another overhand reach forwards.
By contrast, the sidestroke, shown below, involves your entire body being cushioned by the water with every stroke.
The breaststroke also cushions our body with every stroke. We are keeping all movements under the surface of the water. It doesn't matter whether you are using the old frog kick of our youth or the more fashionable whip kick of modern times. All motions are underwater which is the point of exercising in the water.
One of the first strokes we learn as kids is the dog paddle. This is because it is an instinctive stroke. All you do is move your arms and legs forward underwater as if you are trying to run and that motion propels you forward. The only difference between us and the dog is that we can use the legs as much as the arms in our version. We don't use the legs as a drag.
I am not urging you to go out and take swimming lessons. Instead, I am recommending that you utilize your old swimming strokes from the time you were growing up and put them back into use. You will stop stressing your upper body by continually pulling your topmost body and arms out of the cushion of the water. Small matter if you do not remember these strokes perfectly. Moving your arms and legs underwater is what matters no matter how you do it.
There is no "stroke" easier than treading water. You just move your arms and legs in any style you wish although many prefer moving as if they were riding a bike and the more vigorous types as if they were human eggbeaters. The point is that you are moving constantly and with the cushion of the water. In modern times belts are often used around the middle so as to remove any skill worries and so as to just concentrate on the exercise aspect. Others use "the noodle" to help support themselves in the water. It takes very little skill to use either a belt or a noodle but you are maximizing your exercise benefit with either, i.e. win-win. These are shown below.