Getting the point across

I don't recall seeing this on the list of approved navigational signals.

Sailboaters moon Washington State Ferry

Frankly, professional mariners put up with enough guff from recreational sailors, who don't understand some of the limitations of larger craft or the rules involved or the nature of the business, as it is. This sort of thing is completely uncalled for, and probably just makes professional captains and crews that much less likely to extend any courtesy to any of the rest of us when they might have the option to do so.