Types of merchant ships

Depending on their intended use, merchant vessels can be classified as passenger ships, cargo ships, and combined passenger-cargo ships.

Passenger ship

A passenger ship is primarily designed to carry passengers and also handles mail transport, with most operating under time charter arrangements. Its key characteristics include safety, comfort, stability, and speed; its cabins are often elegantly appointed, with excellent ventilation and comprehensive sanitary facilities. It also boasts a relatively high cruising speed.

Cargo ship

A cargo ship’s primary mission is to transport goods, and it is characterized by its economy and practicality. Cargo ships feature spacious holds and are equipped with comprehensive loading and unloading facilities.

Cargo vessels are classified into dry cargo ships and oil tankers according to their respective purposes.

(1) Dry cargo ship. A dry cargo ship is a vessel used to carry dry goods, typically with a deadweight tonnage of 30,000 to 40,000 tons or less; larger vessels are relatively rare. Depending on differences in hull structure and onboard equipment, as well as the types of cargo carried, dry cargo ships can be further classified into:

① A general cargo ship is the most common type of dry bulk vessel and boasts the broadest range of applications. It is primarily used to carry loose, packaged breakbulk cargo. Because breakbulk cargoes are typically shipped in small quantities, general cargo ships tend to be smaller in size than bulk carriers and tankers. They usually operate on regularly scheduled routes with high freight volumes.

② A bulk cargo ship is a vessel specifically designed to carry unpackaged bulk goods.

③ Refrigerated ship is a vessel specifically designed to carry perishable goods such as fresh fruits, meat, and fish. It is equipped with refrigerated holds suitable for storing chilled cargo and high-capacity refrigeration systems. There are two primary refrigeration methods: air‑cooling, which is ideal for transporting fruits, and liquid‑circulation cooling, which is better suited for shipping meat and fish.

④ Timber Ship: a vessel specifically designed to carry timber or logs. Such ships feature large hatchways and interiors free of beams, columns, or other obstructions that might impede loading and unloading; timber can be stowed both in the hold and on deck. To prevent timber on deck from being washed overboard by waves, side bulwarks at least one meter high are typically installed along the ship’s sides.

⑤ A container ship is a cargo vessel specifically designed to carry goods using standardized, reusable containers as its primary means of stowage. Container ships can be further classified into partial-container ships, full-container ships, and convertible container ships. They typically maintain relatively high speeds, ranging from 20 to 26 knots, with some reaching up to 33 knots. Certain container ships are equipped with gantry cranes capable of handling loads exceeding 35 tons; however, most do not carry cranes, relying instead on shore-based lifting equipment for loading and unloading operations. Consequently, the latter type of container ship is often referred to as a “lift-on/lift-off” vessel. In summary, container ships are categorized into three types: partial-container ships, full-container ships, and convertible container ships.

⑥ A Roll On/Roll Off Ship, also known as a Ro‑Ro vessel or a car‑carrier, is well suited for transporting vehicles and heavy machinery, as well as for carrying containers. Its distinctive design features no traditional cargo holds; instead, it has continuous decks running the full length of the ship, often with two to four deck levels. An internal transport system—typically elevators—connects these decks. Moreover, its molded depth—the vertical distance from the main deck to the bottom of the hull—is greater than that of other cargo ships of comparable tonnage. Open ramps at the bow, stern, or on either side of the vessel provide direct access to the quay, enabling cargo to be loaded and unloaded by rolling on and off rather than being lifted by cranes. As a result, this type of vessel achieves faster turnaround times and higher efficiency in both maritime and land‑based operations.

⑦ A barge carrier, also known as a mother‑ship–daughter‑ship vessel, is a type of ship capable of carrying multiple barges, making it well suited for combined sea‑river transport. Such vessels feature a large hull—the “mother ship”—while the barges they carry are referred to as “daughter ships.” Their primary characteristic is that the cargo units are standardized freight barges, with various goods preloaded onto these uniform barges. The mother ship is equipped with a massive gantry crane or a stern‑mounted lift platform; upon arrival at port, these facilities are used to lower the daughter ships into the water. The daughter ships then proceed to inland waterways to load their cargo, return to the mother ship once loading is complete, and finally be re‑embarked onto the mother ship for transit to the final destination port. Upon reaching the destination, the daughter ships are offloaded from the mother ship, thereby completing the operation of transporting the cargo by barge to the inland unloading point. Barge carriers are most suitable for routes connecting ports that are both linked to inland waterway systems.

The most commonly used barge‑carrying vessels are the LASH (Lighter Aboard Ship) type and the Seabee Ship type. The key difference is that the latter’s lighter hull is larger than that of the former, and it can also carry containers. Together, these two types of barge‑carrying vessels are collectively referred to as Kangaroo Ships.

(2) Tankers. A tanker is a specialized vessel designed for the carriage of liquid cargo. Depending on the type of cargo carried, tankers can be further classified into the following two types.

① An oil tanker is a vessel primarily designed to transport liquid petroleum products, including refined petroleum, petrochemical feedstocks, and crude oil. It is characterized by small cargo hatches, excellent sealing capabilities, and an engine room located at the stern. The ship’s hull is divided into multiple oil tanks, interconnected by pipelines, and equipped with air‑compression systems that use compressed air pressure to pump oil into the tanks during loading and unloading. Most oil tanks adopt a longitudinal structure, with a single deck for the cargo hold and longitudinal bulkheads to ensure stability and prevent the cargo from sloshing when the vessel is not fully loaded, which could otherwise lead to capsizing. Oil tankers are typically large‑tonnage vessels, and their size continues to increase; vessels exceeding 200,000 deadweight tons are commonly classified as very large crude carriers (VLCCs).

② A liquefied natural gas carrier is a vessel specifically designed to transport liquefied natural gas. It is equipped with high-pressure liquefied-gas tanks, and to maintain the temperature and pressure within these tanks within specified limits, it also features compressors and condensers.

In addition to the aforementioned types of vessels, there are also hovercraft and hydrofoil boats.

Passenger and cargo ship

A passenger and cargo ship is a vessel that carries both passengers and goods. Some are primarily designed for passenger transport, others for freight, and still others balance the carriage of both passengers and cargo.