Why don't we see his face? As such, I can't tell what he's doing, and I can't really even tell it's a boy. Without the title or challenge, I'd have guessed that this was a man.
interesting perspective/composition- cant really see what is going on with the subject tho his body-language is indicating he is pulling something out of or dropping something into the water? i wish i could see better what he is doing perhaps a different angle? or a rule of 3rds crop might help? my eye keeps going to the blury stick to the right - behind his head... then to his plaid underwear sticking out of his jeans - yep boys will be boys...
right off it doesn't look like a "child", I know there was alot discussion about what a child is but...in this grouping...small children will alway score higher...the shoulders of the shirt appear to be in focus but the rest of the picture seems to be quite soft in the focus...just looking at his back does not engage me...I need to see what he is doing...not just see his back...