Even if you have been active all your life, the things you have done may not be possible now. Running can play havoc with leg joints. Tennis can hurt your shoulders and elbows. The list goes on.
You need a way to stay healthy, without injury, for life.
Fact: Without regularly & safely moving your body, you are more likely to lose your independence & have to rely on others.
None of us wants that.
My method of swimming is for life. Think about trying it.