Originally posted by ThatTimGuy:

For full load, fill your longship hold with iron. Get a friend to ride along with a full inventory with iron. Have that friend harpoon another friend, who has filled their inventory with iron and is waterskiing with a cart, which itself is fully loaded with iron.

Mmmm, iron.

Get another friend with a harpoon, because that will surely attract a sea serpent that will sink the whole lot to the bottom of the ocean.