On Oct 5, 3:48 pm, Joe wrote:

When you visit foreign water, your boat should display a courtesy flag
(the civil ensign of the country you are visiting) whenever your U.S.
national ensign (the USPS ensign or the yacht ensign should not be
displayed in foreign waters) is displayed. (The USPS ensign and U.S.
yacht ensign should not be worn in foreign waters)

Joe,

There is an old drunk on our dock that gave me
a lecture on Flag Etiquette telling me that the
US Ensign was intended to be flown in foreign
waters to inform people it was a non-commercial
vessel. I informed him he was incorrect that only
the US Flag is flown in foreign waters, but the
old gezzer refused to accept my correction and
started to give his whole lecture again.