On june 6th I will be competing in a sprint triathlon. I am a decent runner as well as biker. But have never done any competitive swimming before. As of right now I cant swim more than a couple hundred meters without getting really fatigued. What can I start doing now to prepare my self as much as possible for june 6th. What I have been doing the last couple days is 10x 50m at 50sec with 20sec of rest. Any advise will be greatly appraciated.