Sorry, won't work. Hydrostatic pressure from the weight of the water will force it through the fabric. A taped waterproof trouser leg might work, but not if it has a full lenth zip. You would be better off carrying a wide mouth (easier to fill from a stream or seep) water bladder. Full, of course. <img src="/images/graemlins/smile.gif" alt="" />

P.S. Re the recruit. It would work in S.F. Bay. All he has to do is dive deep enough to gain the momentum needed to get his upper body out of the water.