This article investigates the rules of jurisdiction that were applied in the case of damages in maritime transport. The focus is on traffic in one of the main riverine estuaries of the Low Countries, over the rivers Honte and Scheldt. In the course of the fifteenth century the governments of the county of Flanders and the duchy of Brabant had come to embrace a more exclusive notion of jurisdiction on rivers, which comprised the idea of precise demarcations. In practice, however, this new approach did not bring about more clarity. Uncertainty as to which forum would hear disputes on riverine shipping accidents marked a risk of trade. Among merchants and shipmasters, choice of jurisdiction was common, which happened after mishaps and was not arranged for contractually. The mentioned uncertainty was addressed with rules of thumb, which steered towards the courts of some locations instead of others. They took the port of destination as criterion, in combination with the residence of the merchant-owners of cargo on board of the ship.