Up near the Arctic Circle, the best waterproof parkas are made out of guts.
The Yup’ik of southwestern Alaska work in some pretty unfriendly conditions: temperatures well below freezing combined with punishing wind and snow. If you’re heading out onto the ocean in a kayak you’ll need something light, snug, and waterproof or you’re not going to have a good time of things.
Pre-rubber, latex, and plastic, it’s surprisingly difficult to find genuinely waterproof fabric, and even harder to find something that’s both waterproof and light. The best material available to the Yup’ik for this purpose? Animal intestines.
First, kill a bearded seal, walrus, sea otter, or other marine mammal. Then, extract the intestinal tract – the whole thing. Empty it out, rinse it clean, inflate it like a balloon, and let it dry. Slice up the treated guts and sew them together with sea grass, hair, or animal sinew. Decorate with feathers or fur. The result is a surprisingly practical raincoat.
The Yup’ik gut parka, and the similarly-constructed kamleika of the Aleuts and tuilik of the Inuit, could even create a watertight seal around a kayak and kayaker so that they could roll underwater and come out dry and un-swamped.
[Thanks to Frazer E. for suggesting this topic.]
The Generalist Academy 
You know me, I love me some skin pants