As others have said, the only true fix is to buy a new pair. I am assuming these are neoprene based since it is leaking at the seam. You can silicone it, shoo goo it, etc..., and it may buy you some time, but it won't last forever. If you turn them inside out and look, there will be a strip that runs down the seam on the inside that has been breached. If it is just one small place, I hove bought some of the same stuff they use on the inside (see link below), ironed it on the seam at the leaking spot on the outside, and it will typically patch the one spot. The problem is if it is the crotch area, there are multiple seams, and if they are old you will typically spring another leak someone else after you get the one fixed. If it is on a straight seam or you just have hole on occasion, for $20 the stuff below is worth a shot.