The number of passengers that arrived at or departed from Polish seaport on board of passenger, cargo-carrying ships or ferries, either in international or domestic traffic. The international traffic refers to the number passengers who started their voyages abroad and arrived at a Polish seaport being their port of disembarkation, as well as passengers who started their voyage at Polish seaport on passenger, cargo-carrying ships or ferries, in order to reach a foreign port, during a reference year. The domestic traffic refers to passengers embarked or disembarked at a Polish seaport.