Reysa is a goddess sometimes mentioned in the legends as a patron of explorers by sea. She spends much of her time away from Asgard, travelling and trading in other lands, but her ship, Storrbatr, has been the setting for many great feasts. When onland, she can often be found in the company of her brothers Skjoll and Ølrik.
A Hitch Hiker's Guide to the World Mountain, by Thorin Evenstar
… Of course, if you want to avoid both the portals and the Bifrost, travellings gonna be a lot more difficult. A travel god might manage to go through unaided, provided that Njall the Falcon finds him worthy to travel the mountain passes, but most of us don't have the luxury of being travel gods. If you're really serious, your best bet is to find Reysa, the otter who travels the base of the mountain. While much of her time is spend on the Mountain itself, she keeps a home in Tyr's Holt. It's not much to look at, just a wooden hut on the banks of the river, but it's said that if you wait there long enough, and if she thinks your reasons to travel are good enough, she'll come swimming up to the small dock, and help you wherever you wish to go. Of course, since you're gonna need to keep up with an otter, it's best you know how to swim first.