7 Answers

It is great arobic exercise and it strengthens muscles.

See the 10 health benefits from swimming here:  http://health.howstuffworks.com/wellness/aging/retirement/10-health-benefits-of-swimming.htm

Swimming is the best exercise around!  It works most of your muscles, it burns calories more quickly, it is a terrific aerobic workout as doolittle says, and the most important thing is you can't get a serious injury doing it!   

Swimming`s a great allrounder...improves muscle tone,feel good hormones released..burns calories and helps CVS..(heart and blood flow)...ALSO great exercise for people who have physical disabilities as water supports body...ie you don`t need to be able to walk to enjoy swimming and reap the benefits,treatment made more enjoyable!!

LOW IMPACT, meaning you are not pounding your feet on the pavement and creating shin splints, for example.

Sexy women in bikinis is one of the side benefits on many beaches, especially southern California, Florida, and Hawaii, not to mention those benefits described herein.

It would be of good use to someone who needed to lose weight, probably more so than dieting.  Everyone loves my answers, they always get voted up!