Well, as usual, we really need to get the facts before we judge -- and I think they'll be pretty straight forward.
It is illegal to drink <21 and it is illegal to operate a boat under the influence. Reports say procedure was to handcuff and put on a life vest. Whether it was put on properly will have to be determined. Whether the kid jumped, fell, whatever will have to be determined. I'm not sure I could stand up in a moving boat with handcuffs sober.
I'm sure sorry for the kid and his friends and family. I'm also sorry for the highway patrolman who surely didn't want this to happen or knowingly endanger the kid.