An important part of boating etiquette, and something actually bound to legal norms, is flag protocol. Boats larger than the absolute minimum size always carry at least one flag. The national flag of the country were the boat is registered always has to be present when people are on board, except during the night, when the flag has to be taken in. The national flag has to be attached to a mast at the back, or aft, of the boat. The flag must be clean, with bright, unbleached colors and cannot hang in the water.
Besides the national flag, there are also club flags, which show allegiance to a certain organization, the so-called “jack” flags, which are a special kind of marine variant of the national flag and which are used mostly when boats are not underway, and the courtesy flag, which is used when visiting another country and is a small version of the national flag of the country you are visiting.