Bill's very correct, HI. The depths and techniques that you'll be experimenting with are only attainable with the supervision of a buddy with at least similar skills and the strength to get you back up and to the beach. That said, yes, driving a mouthful of air into your throat or mouth will fool you into thinking life's good and all and maybe get you another 10-15 feet. But again, it's a long-ass haul back up... :naughty
There are a lot of words here and elsewhere about equalizing and other tricks of the trade, i.e, mask pumping, which incidentally I finally got good at last month, that will let you know the rudiments of the skill(s), but after all is read and done, I cannot emphasize enough learning and refining these skills under the eye of a good diver, as in someone with a lot of time and depth. If they're from a recognized freediving type agency, so much the better, but beware here too. The sport is having an influx of what I call the patch and title wearers- those more interested with saying they're Instructors and all, but with barely more game than the student. Ask for references and do the homework. Regardless of how deep and how big the fish is, getting back to the beach is the measure of how good you are.
Hey, Bill! I ordered a couple of masks from AQA and one of their snorkels which looks suspiciously like our revered Farallons! I'll let you know what happens when the Post Office opens.
sven