To get underwater skill, why don't you try some underwater practice? Not to single you out, but does anyone try doing things the old-fashioned way, instead of looking for the quickest, most convenient fix nowadays? --- Through the lights, cameras and action, glamour, glitters and gold I unfold the scroll, plant seeds to stampede the globe when I'm deceased
To gain lung capacity you have to swim underwater.
Your lung capacity will increase by 5% every 200m you swim underwater. The process seems to start slowly but obviously speeds up as you gain more lung capacity when you are able to spend more time underwater.