What does the corpse of the drowned man symbolize?
Esteban (the drowned man who makes such a difference in a town of complete similarity) symbolizes one word: Inspiration.
It is the same inspiration that drives one person to change his life; the inspiration that motivates people to connect to others; the inspiration that brings ones curiosity, and makes one a better person as a result of it.
Alternatively, he represents change. In a town where people had to look at each other to realize that this man was different, his presence (whether dead or alive) was a change to their lives. He was taller, extremely handsome, the grass growing on him was different, even his demeanor (on his corpse's expression) was both different and fascinating to them.
The sense of ownership that both the women and other villagers felt was the same sense of ownership one feels when something unique comes our way, changes our lives, and makes us embrace it. This man, whoever he was, made a difference, without making any changes...just by being him.
Hence, Esteban represents a moment in our existence when we are mysteriously touched by a sense of change and want,belonging, love, and inspiration that makes us want to change.....for no reason at all. That is the magic of Gabriel Garcia Marquez and his works!