Right, get into a crypt ASAP and run back to your boat with the scrap iron. Don't spend any time running around the surface if you can help it.

Bring plenty of arrows to shoot enemies inside the crypts—don't totally destroy the scrap piles when digging into new room, enemies can't path past scrap pile left on the ground so you can shoot them with impunity.

The draugr are going to smash you in troll armor, so be really careful to not let them hit you.

Build a portal at your main base, and then build one on the shore of whatever swamp you are going to crypt dive in. The portal won't let you transfer the ores but will let you get back home for rested, drop off random non-ore loot and just make things tons easier.