When I was in the USCG Auxiliary in Boston in the 90’s they used the same VHF radio as all boaters for most comms, but they also had an encrypted radio they could switch to if they needed to discuss anything sensitive. The encrypted radio was crap though and only worked over short distances. But they’d use it when relaying personal details of boats/people they stopped, dealing with drunk boaters, etc.

As time progressed they switched to using mobile phones when they wanted privacy. Cell coverage along the coast proved far better than the proprietary encrypted radio…