Yeah what he said, swimming is the best and most natural way to build muscle. Because your entire body is submerged in water, EVERY single muscle in your body is being worked as you swim around... The only downside is, not as much. So you're gonna have to swim a fucking ton to feel any burn at the end of the day. Working out is all about damaging and actually ripping the muscles in your body... After you've worked a muscle to the point of failing, you get "the burn." This feeling is your muscles simply healing... and like bones, they grow back twice as strong (Hence muscle growth). For example, I guage my sets and reps upon when my muscles fail.. 1st set: no problem, 2nd set: Things seem heavier 3rd set: I can hardly lift the bar on my final rep...