Thanks, I have stopped biting on to my reg like my life is depending on it and I can breathe easier now as well!I agree with what everyone else has said. It's probably just that you're a new diver and not used to all the exertion. Definitely stayed hydrated. I'd also suggest you make sure your mask isn't too tight, and try not to bite so hard on the regulator mouthpiece. And relax! You're on vacation, after all.