Good topic for discussion.

I was going to comment that swimming doesn't increase bone mineral density, but apparently it can be helpful in some situations. Who knew!

I tried posting the link to a study but since I'm a newer member I apparently can't post links yet. But you can search for "Swimming as Treatment for Osteoporosis: A Systematic Review and Meta-analysis" on the NIH site.

From the Conclusions: "Although more clinical randomized controlled trials are needed to study the effect of swimming on BMD in other parts of the human body, we have preliminary evidence to show that swimming may have an effect on the lumbar vertebra density of premenopausal swimmers and that swimming may improve the BMD or the radius in these participants. This may also be a good program for the clinical prevention and treatment of osteoporosis."