A waterproof slide type fastener or zipper assembly featuring side by side tape means the adjacent edges of which mount cooperatively designed interlocking loops or coils wherein the tapes and loops are coated and filled with a resilient material in the nature of a room temperature vulcanizable silicone rubber compound. The arrangement is such that the interlocking of the loops on the respectively adjacent edges of the tapes, through the medium of a slide type closure element, causes a compression and sealing adherence of the contained resilient material which forms a releasable but positive seal and bond between the parts. The energy stored in the compression of the resilient material insures against passage of water in the vicinity of the interlocking loops while permitting their ready separation, as and when required. The invention also contemplates a simple and inexpensive way of using vacuum to apply the resilient material to the loops or coils and their connected tapes.