PNewflie, our govt. requires that passengers clear through immigration
if the ship has stopped at a FOREIGN port prior to stopping at a U.S. port.
Example-- If a ship leaves Miami , stops in the Bahamas and then goes on to a U.S. port ( normally St. Thomas ) then the passengers have to clear through immigration.
Some folks let it irritate them but like it or not, it's the law and if everyone cooperates and goes as they should, it doesn't take long to clear the ship.