Seagoing commercial vessels

Two modern container ships in San Francisco

Commercial vessels or merchant ships can be divided into four broad categories: fishing, cargo ships, passenger ships, and special-purpose ships.^[46] Modern commercial vessels are typically powered by a single propeller driven by a diesel or, less usually, gas turbine engine.^{[citation needed]}, but until the mid-19th century they were predominantly square sail rigged. The fastest vessels may use pump-jet engines.^{[citation needed]} Most commercial vessels have full hull-forms to maximize cargo capacity.^{[citation needed]} Hulls are usually made of steel, although aluminum can be used on faster craft, and fiberglass on the smallest service vessels.^{[citation needed]} Commercial vessels generally have a crew headed by a captain, with deck officersand marine engineers on larger vessels. Special-purpose vessels often have specialized crew if necessary, for example scientists aboard research vessels.

Fishing boats are generally small, often little more than 30 meters (98 ft) but up to 100 metres (330 ft) for a large tuna orwhaling ship. Aboard a fish processing vessel, the catch can be made ready for market and sold more quickly once the ship makes port. Special purpose vessels have special gear. For example, trawlers have winches and arms, stern-trawlers have a rear ramp, and tuna seiners have skiffs. In 2004, 85,800,000 tonnes (84,400,000 long tons; 94,600,000 short tons) of fish were caught in the marine capture fishery.^[47] Anchoveta represented the largest single catch at 10,700,000 tonnes (10,500,000 long tons; 11,800,000 short tons).^[47] That year, the top ten marine capture species also included Alaska pollock, Blue whiting, Skipjack tuna, Atlantic herring, Chub mackerel, Japanese anchovy, Chilean jack mackerel, Largehead hairtail, and Yellowfin tuna.^[47] Other species including salmon, shrimp, lobster, clams, squid and crab, are also commercially fished. Modern commercial fishermen use many methods. One is fishing bynets, such as purse seine, beach seine, lift nets, gillnets, or entangling nets. Another is trawling, including bottom trawl. Hooks and lines are used in methods likelong-line fishing and hand-line fishing. Another method is the use of fishing trap.

Cargo ships transport dry and liquid cargo. Dry cargo can be transported in bulk by bulk carriers, packed directly onto a general cargo ship in break-bulk, packed inintermodal containers as aboard a container ship, or driven aboard as in roll-on roll-off ships. Liquid cargo is generally carried in bulk aboard tankers, such as oil tankers which may include both crude and finished products of oil, chemical tankers which may also carry vegetable oils other than chemicals and LPG/LNG tankers, although smaller shipments may be carried on container ships in tank containers.

Passenger ships range in size from small river ferries to very large cruise ships. This type of vessel includes ferries, which move passengers and vehicles on short trips; ocean liners, which carry passengers from one place to another; and cruise ships, which carry passengers on voyages undertaken for pleasure, visiting several places and with leisure activities on board, often returning them to the port of embarkation. Riverboats and inland ferries are specially designed to carry passengers, cargo, or both in the challenging river environment. Rivers present special hazards to vessels. They usually have varying water flows that alternately lead to high speed water flows or protruding rock hazards. Changing siltation patterns may cause the sudden appearance of shoal waters, and often floating or sunken logs and trees (called snags) can endanger the hulls and propulsion of riverboats. Riverboats are generally of shallow draft, being broad of beam and rather square in plan, with a low freeboard and high topsides. Riverboats can survive with this type of configuration as they do not have to withstand the high winds or large waves that are seen on large lakes, seas, or oceans.

The Albatun Dos, a tuna boat at work near Victoria, Seychelles

Fishing vessels are a subset of commercial vessels, but generally small in size and often subject to different regulations and classification. They can be categorized by several criteria: architecture, the type of fish they catch, the fishing method used, geographical origin, and technical features such as rigging. As of 2004, the world's fishing fleet consisted of some 4 million vessels.^[41] Of these, 1.3 million were decked vessels with enclosed areas and the rest were open vessels.^[41] Most decked vessels were mechanized, but two-thirds of the open vessels were traditional craft propelled by sails and oars.^[41] More than 60% of all existing large fishing vessels^[48] were built in Japan, Peru, the Russian Federation, Spain or the United States of America.^[49]