Torres Straight Islander canoes. When a man requires a canoe, he sent word and a part payment in shell ornaments to a trading partner to the north. The request and payment would be passed from one trading partner to another until it reached the mouth of the Fly River, Papua New Guinea where wood was available to make canoe hulls. Eventually, a hull came back via the same relay system. Double outriggers and other features were added en route until it reached the original purchaser. If satisfied, he would send further repayments for the next three years.