Hi welcome to HCM
I have gone thru your query regarding "swimming stamina be available while doing other exercises".
Dear , swimming involves your lungs legs hand in fact your whole body so helps build your endurance which can be used in other workouts as well . Growing stamina in swimming is not for swimming only.
is of course , a good way to build stamina for tennis when you aren't playing too often .
You can do this in any context: tennis, swimming, biking, running, that is gentle on your joints, although obviously it won't help with your hand eye coordination for tennis .
Pranayam &
Yoga is reputed to be very beneficial for gaining strength all over your body
specially pranayam - deep breathing help build endurance .Every time you breathe in, your belly should fill up like a balloon, . And every time you breathe out, that balloon should deflate.
When you take a breath, 80 percent of the work is done by the diaphragm. Slow and deep breaths help strengthen your diaphragm .
If you strengthen your diaphragm, you may improve your endurance and be less likely to become fatigued." It helps in swimming also .
Hope this helps solve your query Take care All the best