Wookie,
At least in this state if you operate a commercial charter you agree to be search by fish and game (among others). This is stipulated on your state permit to actually operate a commercial fishing charter leaving and returning from Washington ports. All of our divable water's are state waters, so you remain under state jurisdiction - so you can't tell local law enforcement to "eff off" and that you'll only deal with the Coast Guard. The Sheriff's marine patrol(s) and city's with marine or harbor patrol units most definitely have jurisdiction aboard all the local dive vessels. We have thousands of documented vessels in this state (many commercial, many inspected) and just having a licensed master aboard does not give any of them the right to refuse compliance with local authorities. Our charters (what few remain after the economic crash) are operating exclusively in state waters on coastwise voyages only. I doubt any of them are remotely SOLAS compliant or in any way prepared to be a floating "state". Nevermind that I can't think of a single dive wreck outside even the 3 mile limit. Three miles out is like 600+ft deep.
We used to have one international charter operating between both the US and Canada, but he moved his boat (Nautilus Explorer) to the Socorros. That would be the only dive vessel in recent memory I can think of potentially able to successfully claim he was operating outside of local authority. There are foreign flagged crusie ships departing from Seattle for AK, but these are obviously not dive (or fishing) charters. But they also aren't searching passengers for GPS's.
Only a fool for a fishing or dive charter skipper here would try to excercise bodily search authority even for contraband. Deny boarding if you're at the dock, or radio ahead for LEOs to meet you someplace if underway. Even if you were "in the right", the court of public opinion would crucify you for the perception of inappropriate contact just like they do for TSA pat downs of grandmas and 3yos. Besides, after 10 years of "medicinal" use, recreational pot is legal in Washington now lol.