When docking in port, you can choose to book a guided shore excursion (there are plenty to choose from at every destination) or catch a transfer into town and explore on your own. You can also opt to stay onboard the ship, which some people choose to do if they have visited the destination previously. The advantage to staying onboard is that you will practically have the ship to yourself – the pool will be far less crowded, spa treatments may be on special and there will be no lines at restaurants and bars.