From what I can tell from the article below, these guys were riding trails and river banks before one of the poor bastards swamped his ATV only to then watch it float down river (and I'll assume the second guy stopped laughing his ass off once the officer's focused their attention on him). So maybe they had been drinking, but if that's the sole basis for the DWI arrest, these officers missed the mark. While you can be arrested for DWI on an ATV, you have to be operating it (or have operated it) on a public roadway in order to be subject to VTL1192. There is no set of DWI laws unique to ATV's like there is for boats (i.e., NYS Navigation Law Sec. 49-a).
Unless there's more to the story, I have a feeling these guys will be looking at non-alcohol related dispositions at the end of the day, which should help buy that replacement ATV!