I think you are saying that we should encourage swimming? Certainly it is good that people know how not to drown, but swimming itself unless very energetic, does not do that much your your cardio-vascular system. However, I agree, some exercise of any sort is better than slobbing around eating too much! The view in UK with regard to sea swimming is "You can't really swim in the sea - you can only go through the motions".
Swimming is excellent exercise. That is swimming not just bobbing in the pool!
Gentle cardiovascular workout. Elongating all muscles so no muscle ache afterwards; the water supporting all limbs so joints don't get overstrained etc.