The protagonist uses this mode of traveling to reach the cave of a creature whom he decapitates with a sword made for giants.
A character is improbably described as doing this activity while "shouldering thirty battle-dresses," which he does to escape after his uncle is killed. A character describes how he engaged in this activity for seven nights in the "perishing cold," during which he battled and killed nine monsters. In a flyting scene, Unferth notes that the protagonist was defeated in this sort of contest by his childhood friend (*)  Breca. The protagonist uses this mode of traveling to reach the cave of a creature whom he decapitates with a sword made for giants. That hag, whose lair is only accessible by this mode of travel, had a son who terrorized Hrothgar's hall. For 10 points, Beowulf excels at what mode of travel, which he uses to reach the home of Grendel's mother in a lake?
A character is improbably described as doing this activity while "shouldering thirty battle-dresses," which he does to escape after his uncle is killed.
swim ming [or  diving ; accept word forms of either answer]