What does the lake symbolize in T.C. Boyle's "Greasy Lake"?

The lake of T.C. Boyle's story "Greasy Lake" symbolizes the changing perceptions of the narrator.

In the beginning of the narrative, the lake represents a spot that is secluded from "the world of 'do-gooders'" where teens can secretly engage in illicit behavior and escape the consequences. However, the pretense of safety in dangerous behavior becomes perilous itself as the narrator and his friends find themselves confronted with serious injury when in their drunkenness they mistake a car for that of a friend's. Instead of their friend Tony emerging from the car, "a bad greasy character" with steel-toed boots confronts the boys, and inflicts serious injury upon them. After the narrator pulls out a tire iron, he and his friends defeat their foe. Then, they turn their attention to the girlfriend, who comes shrieking out of the other car. Now, their minds turn from violence to lust as they try to assault her.

But, headlights coming toward them arrest their actions and send the narrator wading into the lake as he flees what he thinks may be the police. As he wades deeper, thinking to plunge under the water, the narrator senses that he has blundered onto "another greasy character." This one fills him with horror. This is "greasy primitivism" at its lowest, for it is a dead body. With an illuminated perception, the narrator realizes the foolishness of his and his friends' behaviors. He acknowledges with a new maturity from this experience that there are dire repercussions to illicit conduct. 

Further, as he listens, the narrator hears the cursing of the "greasy character" that he and his friends have beaten. This "greasy character" and a buddy, who has pulled up, call out to the narrator and his friends. When there is no response, they decide to strike the station wagon with a tire iron, breaking the windshield and seriously damaging the body of the vehicle. Then they pull away. Quickly, the boys hurry back to the station wagon and are able to escape after the narrator suddenly spots his keys. As the vehicle hobbles along, the narrator notices that "[T]here was a sheen of sun on the lake," symbolizing his enlightenment.

The Greasy Lake to which the boys have come as a shelter from the consequences of bad behavior has transformed itself in their perceptions to a place of horror. Yet, in experiencing this horror, the narrator, at least, has matured and "seen the light" of acting morally.