There is a strict protocol used by sailors when entering a new country for customs and immigration. When entering the territorial waters of a new country that you plan to make a stop in you must fly a yellow flag. This flag is called the Q-Flag or Quarantine Flag. You must leave the Q-Flag up until you have checked into immigration and customs in the new country. Once you are checked in you raise the flag of the country you are visiting. Most sailors also fly the flag of their own county somewhere on the boat.
This is Don raising the Azores flag after we arrived and got checked in. The flag on the top is Portugal and the flag on the bottom is the Azores.
