you are subject to maritime laws if you decide to go boating. and you also agree to random searches (safety inspections). most coast guards, LEO's really just want to do their job and go home. but there are a few who are a little gung-ho and believe they are fighting the war themselves.
Our Customs Service is also exempt from our Constitutional safeguards concerning the 4th Amendment – but there was a restriction on how far from the boarders or coasts were free to operate. It wouldn’t take much for this to be expanded, and one customs agent with a squad of other LEO personnel would still be covered if the Customs agent was in charge.