It looks like someone didn't properly register his sailboat and is entitled to be ticketed for it:
"In Alabama, all mechanically propelled vessels, sailboats, and boats for hire must be registered, but there are a few exceptions to this law:
A vessel operating under a temporary number.
A vessel already covered by a number in full force, such as that of another state, provided the vessel has not been in Alabama more than 90 days.
A vessel temporarily using Alabama waters that is under registry from another country.
A vessel owned by the United States, a single state, a county, or a municipality.
A ship's lifeboat.
A vessel not propelled by machinery except for sailboats and rental boats. "
From Alabama Boat Registration Procedure, Forms, & Information - DMV.ORG
Alabama apparently requires sailboats to be registered "T/T" or otherwise. The fact that the larger boat was documented does not excuse wither vessel from "motor vehicle" laws requiring registration of the motor vehicle. He might be able to plead that the sailboat IS his lifeboat, and that he was teaching the yl how to use the lifeboat, and get that ticket dismissed.
But the charge for DUI? The cop is going to say the boat was being operated erratically and that's why they came over. It probably was erratic, because a student was operating it. Either way, the DUI charge is serious these days, you want a local attorney for that one. You might be able to get that dismissed if you can substantiate some defect or convince the judge that the yl was not "operating" the boat, she was just being "shown" the operation of the boat. (Not to conflict what what is said about using the lifeboat though!)
I don't see Gestapo or Pigs here. I see an overreaction to good enforcement against drunk boating. If they see a boat operating erratically, they MUST check into it. If you are drinking while boating, you may say you aren't drunk--but that's why pilots have a "24 hours NO alcohol" preflight policy. Sounds like they could have been way harsher and the watercops only did what they are supposed to do--and properly at that.
If someone tells me they had to hide the beer--to me that means they KNOW it shouldn't have been there.