Well, actually in NH you do need a boating certificate to operate legally.
And boaters do get arrested for DWI. Lake Winni is heavily patrolled, so
drunken boaters will get caught.

But I get your point; drunken boaters are a hazard.

By the way, when a private pilot gets into his/her plane, who checks to
see if he/she is drunk or otherwise intoxicated? Two years ago, right
here in my little state of New Hampshire, a guy got drunk, had an
altercation with the cops, got a restraining order against him, and then
flew his plane from Nashua Airport into his wife's house! Its on the NTSB
website. One of my favorite stories.....