Answer:
The lake is described as dark, gloomy and disgusting.
Step-by-step explanation:
Grendel's mother lives in an underwater lair in a set of lakes and swamps that is described in an uncomfortable and unpleasant way. Lines 422-440 describe this place as an environment formed by decomposition, rot and darkness and show the lake as a very unpleasant place. This contributes to increasing the inadequacy tone and provokes, in the reader, a feeling of regret in relation to Grendel and his mother. In addition, this environment reinforces the concept of disorder, caused by the two monsters.