This is a horrible, horrible situation, every parent's worst nightmare.
It was a accident, the young man did not intend to get hurt.
But lessons can always be learned. I was a life guard and water safety instructor and pools are dangerous. It only takes inches to drown.
There is absolutely no blame to be put on Disney. Their lifeguards are some of the most diligent and trained I have seen.
It is swim at "your own risk" when lifeguards are not there, just as it is at most all hotels that don't even have lifeguards at all. It would be so expensive to have guards there all the time, so the solution would be to make room rates higher or close pools completely when no guard is there.
Parents and individuals have to assume that risk.
As a parent, you can teach your child that pools are dangerous. That you don't run, you don't dive, and you don't rough house and you have a buddy system.
Drowning victims make no noise: This is a great article that everyone especially parents need to read.
http://mariovittone.com/2010/05/154/
And out of respect and memory of this young man, learn something from this, and do not ever send a small child to a pool without a parent. The things I have seen at Disney pools make me shudder.
Prayers for all of us family.