I'm working on losing 30 pounds by November and have switched to swimming as my daily cardio routine.

A few months ago, I did a couple 5k runs and was getting excited about making improvements in my running performance. My main problem was that running was taking a terrible toll on my body: joints hurt, muscles and tendons straining and on top of that, I couldn't even keep up this routine everyday! I'd spend the whole day psyching myself up for a run even if I was only running 3x a week.

Fast forward to today, I tried out swimming because I have access to an olympic sized pool near my work and wanted to get back into a good workout rhythm after a recent illness. I found that swimming solved all of the problems I had with running and it is a lot of fun!

TL;DR - If you want some easy-on-the-body cardio, swimming is pretty damn awesome!