Water skin

From Trail-Finder -- Dedicated to getting you outside

Water skins are a way of carrying water which used to be very popular, but was largely replaced long ago, first by canteens, then by hard plastic water bottles, and most recently by water bladders in hydration packs. They are still available, however newer water skins are more like hydration packs, in that they are water bladders inside a traditional, often synthetic, skin.