It's always worse to see the blame game. Stupid really.
It's the law you know, underage drinking. It's not something that people go to jail for until they are operating a boat or car, etc. Anyone suspected of driving under the influence should be arrested. That's the way laws work, you break them, you get in trouble. It's real simple. Underage drinking is not a right that you have because a lot of people do it. That's ignorance.
Yes you are correct that if he didn't arrest him then he might still be alive or possibly he could have ran through the middle of another boat and a whole bunch of people could have died. And then you would be complaining about the Water Patrol not doing their job. So which is it? Should they be out there patrolling or not?