Let me add a couple points to PapaBill's good explanation about tendering. The size of your vessel is also a factor. There are ports which can accommodate small to medium sized ships at the dock, but megaliners will have to anchor offshore. If the sea is too rough, the captain may decide to cancel a port call altogether rather than risk the passengers' or crew's safety. So keep in mind that you may not get to visit a particular port if conditions don't permit. If you do tender to shore, it's also possible you'll be unable to return later. That has happened to people on rare occasions, even when it means staying on the beach all night without shelter. Always block off extra time to reboard the ship when you must take a tender and try not to plan on using the last one or you might have a longer wait.