A ship's tender, usually referred to as a tender, is a boat used to service a ship, generally by transporting people and/or supplies to and from shore or another ship. Smaller boats may also have tenders, usually called dinghies.
For a variety of reasons, it is not always advisable to try to tie a ship up at a dock; the weather or the sea might be rough, the time might be short, or the ship too large to fit. In such cases tenders provide the link from ship to shore, and may have a very busy schedule of back-and-forth trips while the ship is in port.
On cruise ships, lifeboat tenders do double duty, serving as tenders in a day-to-day activities, but fully equipped to act as lifeboats in an emergency. They are generally carried on davits just above the promenade deck, and may at first glance appear to be regular lifeboats; but they are usually larger and better-equipped. Recent ships tend to favor catamaran designs, since they are less likely to roll in the calm to moderate conditions in which tenders are usually used. They typically carry up to 100-150 passengers and 2-3 crew.