In an ideal world, every cruise ship would be able to tie up to a pier on port calls for easy disembarking. But this just isn't possible. Some ports have shallower or narrow waterways that would make navigation tricky or impossible for passenger ships. And some cruise ships are too large and have too deep of a draft to access ports that can more easily accommodate smaller vessels.
When docking is not an option for a cruise ship, it will anchor in the deeper water offshore, and use smaller boats, called tenders, to get passengers to and from shore. The process is also referred to as tendering.
On larger cruise ships, tender boats are specifically designed to carry groups of passengers to and fro, with safety and stability in mind. They are often covered or enclosed, offering passengers protection from the elements. They are usually flat bottomed, providing maximum stability for passengers during boarding and off-loading. They also often do double-duty, serving as lifeboats in case of an emergency.
On smaller ships, the tender boat may be simpler and open-air. This is the case when the distances covered from ship to shore are shorter, or when the passengers tend to more adventurous. Expedition ships often use Zodiac boats to tender passengers to shore, either for a dry landing at a pier or a wet landing, where passengers need to jump from the Zodiac into the shallow waters of a beach to wade to shore.
A port is designated to be a tender port based on the cruise ship specifics, not the port itself. Some ports have piers that can accommodate small cruise ships, but require larger mega-ships to tender passengers in to solid ground.
