Maritime transport (or ocean transport) and hydraulic effluvial transport, or more generally waterborne transport, is the transport of people (passengers) or goods (cargo) via waterways. Freight transport by sea has been widely used throughout recorded history. Water transport is highly cost effective with regular schedulable cargoes, such as trans-oceanic shipping of consumer products – and especially for heavy loads or bulk cargos, such as coal, coke, ores, or grains. Ships and other watercraft are used for maritime transport. Types can be distinguished by propulsion, size or cargo type. Recreational or educational craft still use wind power, while some smaller craft use internal combustion engines to drive one or more propellers, or in the case of jet boats, an inboard water jet. Most modern merchant ships can be placed in one of a few categories.

Bulk carriers are cargo ships used to transport bulk cargo items such as ore or food staples (rice, grain, etc.) and similar cargo and can be recognized by the large box-like hatches on their deck, designed to slide outboard for loading. Container ships are cargo ships that carry their entire load in truck-sized containers, in a technique called containerization. They form a common means of commercial intermodal freight transport and they carry the majority of the world's dry cargo. Cruise ships are passenger ships used for pleasure voyages, where the voyage itself and the ship's amenities are considered an essential part of the experience. A multi-purpose ship (sometimes called a general cargo ship) is used to transport a variety of goods, from bulk commodities to break bulk and heavy cargoes. They are usually geared (supplied with cranes), and modern examples are fitted for the carriage of containers and grains.An ocean liner is a passenger ship designed to transport people from one seaport to another along regular long-distance maritime routes according to a schedule. Refrigerated ships (usually called reefers) are cargo ships typically used to transport perishable commodities which require temperature-controlled transportation, mostly fruits, meat, fish, vegetables, dairy products and other foodstuffs. Roll-on/roll-off ships are ships designed to transport wheeled cargo such as automobiles, trailers or railway carriages. RORO (or ro/ro) vessels have built-in ramps which allow the cargo to be efficiently "rolled on" and "rolled off" the vessel when in port. Tankers are cargo ships for the transport of fluids, such as crude oil, petroleum products, liquefied petroleum gas (LPG), liquefied natural gas (LNG) and chemicals, also vegetable oils, wine and other food. The tanker sector comprises one third of the world tonnage.

A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. Most barges are not self-propelled and need to be moved by tugboats towing or towboats pushing them. Cable layer is a deep-sea vessel designed and used to lay underwater cables for telecommunications, electricity, and such. A large superstructure, and one or more spools that feed off the transom distinguish it. Coastal trading vessels, also known as coasters, ships used for trade between locations on the same island or continent. They are often small and of shallow draft, and sometimes set up as self-dischargers. A dredger (sometimes also called a dredge) is a ship used to excavate in shallow seas or fresh water areas with the purpose of gathering up bottom sediments and disposing of them at a different location. Ferries are a form of transport, usually a boat or ship, but also other forms, carrying (or ferrying) passengers and sometimes their vehicles. Ferries are also used to transport freight (in lorries and sometimes unpowered freight containers) and even railroad cars. A tugboat is a boat used to manoeuvre, primarily by towing or pushing, other vessels (see shipping) in harbours, over the open sea or through rivers and canals. They are also used to tow barges, disabled ships, or other equipment like towboats. Open hatch general cargo ships are designed to transport forest products, bulk cargos, unitized cargoes, project cargoes and containers. Semi-submersible heavy-lift ships often move particularly large, heavy, or bulky goods that other ships cannot handle well. Such off-size goods include ship hulls, premade construction materials, other seagoing vessels, power plant components, cast steel objects, and a variety of very large or heavy goods.

For a port to efficiently send and receive cargo, it requires infrastructure: docks, bollards, pilings, cranes, bulk cargo handling equipment, and so on – equipment and organization supporting the role of the facilities. From pier to pier these may differ, one dock handling intermodal transport needs (container-ships linked to rail by cranes); another bulk handling capabilities (such as conveyors, elevators, tanks, pumps) for loading and unloading bulk cargoes like grain, coal, or fuels. Others may be outfitted as passenger terminals or for mixed mode operations. Generally, Harbors, seaports and marinas all host watercraft, and consist of components such as piers, wharfs, docks and roadsteads.