What does it mean if you dream of your sons friend died from drowning?

Two basic principles can guide all dream interpretation: dreams use symbols, and dreams are about the dreamer. Although this dream appears to be about the dreamer's son's friend, one needs to look for how the images in the dream relate to the dreamer. The "friend" of the son might actually represent the dreamer, as the parent wants to be a "friend" to the son. Drowning usually represents feelings of being overwhelmed. So the meaning of the dream might be that the dreamer longs to be a friend to the son, but feels overwhelmed by the effort.