Nettle actually spins a very fine thread and it weaves a beautifully fine and strong white cloth. That whiteness means that unlike flax and hemp it doesn't need bleaching.
It's a beautiful fabric
It waterproofs just like any other bast fibre fabric.
The weave is the crucial element though. Tightly spun and woven cotton makes ventile which is naturally showerproof, but soft spun and gently woven makes denim and towels which soak up water like a sponge.
cheers,
Toddy