I think the only reason I'd want a zipper is for takin' a leak. Otherwise, why pay for it? It would be nice not have to take off a jacket, vest and whatever else. Don't think I'm there yet though... I've used drysuits for various purposes for several years. The only time I've had a zipper leak was when I didn't have it zipped all the way. THAT was eye-opening..... Given quality construction, there's no reason a waterproof zipper should leak.