OK I'll get out there and see what kind of blends I can come up with. Straight linen is probably going to catch the wind too easily, which is something that is abundant on a sailboat. Something with some wool in it and a bit of weight should do nicely.

I imagine woad was probably one of the natural dyes, and IIRC I think indigo comes up with almost the same shade of blue even though indigo itself was not available until much later. But I might actually be able to score indigo dye so I'll look down that route.

Thanks muchly Matt. I'll send you a pic when I'm all done up in the Viking garb.