Other mistake: When Beowulf and the Geats discover the cave which hides the entrance to the Sea Hag's cave, there is a light shining up through the pool of water as though it opens up to sunlight on the other side. When Beowulf swims through to the other side however, he emerges into another equally dark cave. A bright clear light is still shining from under the water though. Both sides of the water tunnel open into dark caves. There is no light source, yet the light shines just the same on both sides.