I'm not seeing much in that description of the border exception that would touch this vessel, which appears to be something akin to "at port," much less a vessel controlled by a company with as many legal resources as Google. It would be a shitshow if the USCG just stormed in there.
Ask any boater how any interaction with the Coast Guard goes. They wield an incredible amount of power in search and seizure and centuries of court precedence. Unlike the TSA they are pros at security theater, even if you think you are right you are almost always wrong.
The barge is not in a lake, it's in a bay and border rules take precedence.