A seaport is a facility which can accommodate ships which go out to sea. Seaports can be found in natural and artificial harbors along many coastlines in the world, and they have a variety of fixtures including cranes to help ships handle cargo, and docks for ships to attach to. Seaports are of economic and strategic importance to the nations which hold them, because they can be used for everything from shipping out a nation's consumer products to loading up troop ships to sail to war.
Ports can also be found in inland waters such as lakes and rivers, but they are not known as seaports because they do not have facilities for seagoing ships. In some cases, inland ports have no outlet to the ocean, and in other instances, the waterway may not be navigable by oceangoing ships. Not all seagoing ships can fit in a seaport, either: large oil tankers, for example, actually dock offshore while smaller tenders load and offload their cargo.
A typical seaport includes equipment and facilities for handling and storing cargo, such as warehouses and cranes, along with amenities which are designed to appeal to people coming into port, such as restaurants and hotels. Ship building and repair companies are typically located near ports for the convenience of their clients, and sea ports may also have facilities for quarantine and other special needs; a well-designed port may allow people to get everything they need without straying more than a few blocks away from their ship.
Some seaports are primarily focused on cargo and commercial trade, while others cater to passenger boats like cruise ships, and many provide facilities for a mix of uses. People may also be able to dock personal craft such as sailboats at a seaport so that they will have ready access to the ocean. Offices of shipping companies, harbor masters, pilots, and tugboat businesses are also classically located next to the port for convenience.
The strategic importance of a seaport can change over time. Some ports have been lost due to erosion or other issues which have caused the port to vanish or become innavigable. Others have become less important because they are no longer on major trade routes, or because a nation's production of cargo has declined, making the port less profitable for shippers. The most valuable ports tend to be warm water ports, in which the water in and around the port does not freeze in the winter, allowing the port to be used year-round.