Crossing rivers and boggy ground would have presented a number of dangers to early Scandinavians. There is a good deal of mythological evidence that Þórr is associated with the challenges of travelling by sea, as well as on various kinds of watery situations on land, such as rivers, lakes and bogs. There is literary evidence for the invocation of Þórr in seafaring, and this paper hypothesises that Þórr was invoked in related activities of crossing rivers and wet ground. The paper demonstrates a strong geographical relationship between Þórr-worship (as shown by settlement place-names) and crossing rivers and marshes (as shown by runic inscriptions commemorating bridges and fords), and attempts an explanation of this relationship in terms of the mythological evidence.