Question: What is the lightest waterproof material available and how much does it cost?

Conor Cullen answered on 15 Nov 2016:

This is a good question!

So it depends really on what you want to use it for. To be technically correct I’d say the answer graphene, this is a two-dimensional material made up just of carbon atoms connected together in a big sheet, its only one atom thick and so weighs almost nothing and you use so little carbon that its effectively free. Graphene is also a great barrier and so is waterproof.

If you wanted to be a bit more practical and wanted to build a boat out of something today id say if all you were thinking about was being light and waterproof then plastic would be the way to go.