Cargo ships are classified into various types on the basis of purpose, size, type of cargo, etc. 

The economic factor is of prime importance in designing a merchant ship. Every owner wants maximum return on their investment.

Ships are mainly classified into the following types:

1. Container Ships:

A vessel structured specifically to hold huge quantities of cargo compacted in different types of containers is referred to as a container vessel (ship). 

2.  Bulk Carrier:

Bulk carriers are a type of ship which transports cargoes (generally dry cargo) in bulk quantities.

The cargo transported in such ships is loose cargo i.e., without any specific packaging to it and generally contains items like food grains, ores and coals, and even cement.

Some other forms of dry cargo are:

3. Tanker Ships:

These are for carrying a large amount of liquid cargo. Tankers are further sub-divided into different types on the basis of the cargo they carry.

The main types of tankers are:

Oil Tankers: Oil tankers mainly carry crude oil and its by-products

Liquefied Gas Carriers: A gas carrier is a ship designed to transport LPG, LNG, or liquefied chemical gases.

Chemical and Product Carriers:
A chemical tanker is a type of tanker ship designed to transport chemicals and different liquid products in bulk.

On the basis of their size, tankers are further divided into various types such as:

VLCC, ULCC, Panamax, Aframax, Suezmax, etc.

4. Passenger Ships:

These are mainly used for transiting passengers.

They are mainly classified into:

Ferries- Vessels used for transiting passengers (and vehicles) on short-distance routes.

Cruise Ships- Mainly used for recreational activities are like luxurious floating hotels.

5. Roll-on Roll-Off Ships:

Ro-Ro is an acronym for Roll-on/roll-off. Ro-Ro ships are vessels that are used to carry wheeled cargo. 

• Pure Car Carrier (PCC) and Pure Car and Truck Carrier (PCTC) RoRo Ships 

• Container Vessel + Ro-Ro (ConRo) Ship 

• General Cargo + Ro-Ro Ship (GenRo) Ships 

• RoPax 

• Complete RoRo Ships 

6. Offshore Ships:

Offshore vessels mainly help in oil exploration and construction jobs at sea. Offshore vessels are of several types. 

  Some of the main ones are: 

1. Supply Ship: Vessels that supply to offshore rigs 

2. Floating cranes: A vessel with a crane specialized in lifting heavy loads. 

3. Drill Ships: A drillship is used in exploratory offshore drilling of new oil and gas wells. 

4. Accommodation Barges 

5. Production Platforms: To extract and process oil and natural gas, or to temporarily store product. 

6. Floating Storage Unit (FSU) – Floating vessel mainly used for storage of oil and by-products.  

7. Floating Production and Storage Unit (FPSO): This vessel is used for the production and processing of hydrocarbons, and for the storage of oil. 

8. Anchor handling vessels – These are used for offshore construction and installation operations. 

9. Diving vessels – These are vessels used by divers for diving in the ocean for underwater jobs. 

7. Fishing Vessels:

Vessels used for fishing at sea.  

Fishing vessels are mainly classified into two types – trawlers and non-trawling vessels. 

• Trawlers: A fishing trawler is a commercial fishing vessel designed to operate fishing trawls. Trawling is a method of fishing that involves actively dragging or pulling a trawl through the water behind one or more trawlers. 

• Non-Trawling vessels: Nontrawling vessels range from a simple craft to vessels that can lay nets that are kilometers long. These nets have to wait for the fish to swim into the net.

• Factory Ships: A factory ship, also known as a fish processing vessel, is a large ocean-going vessel with extensive onboard facilities for processing and freezing caught fish. 

8. Speciality Vessels:

Specialty vessels are constructed and used for specific purposes. 

Tugs: A tug (tugboat) is a boat that manoeuvres other vessels by pushing or towing them.  

Tenders – A boat or a larger ship used to service or support other boats or ships, generally by transporting people and/or supplies is called a tender vessel.

Cable Layers – Cable laying vessels help in laying cables onto the sea bed. 

Research Vessels – Vessel used for carrying out a variety of research at sea. Some of the most common types of research vessels are – hydrographic vessels, oceanographic vessels, polar vessels, etc. 

Salvage Vessels – Salvage vessels are vessels engaged in the salvage operation. 

Lightships: A light vessel, or lightship, is a ship that acts as a lighthouse. They are used in waters that are too deep or otherwise unsuitable for lighthouse construction. 

Pilot Crafts – Pilot crafts are used for the transportation of harbor pilots. 

Barge Carriers: A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. 

Timber Carriers: Vessels that carry timber 

Livestock Carriers: Vessels that carry livestock/animals 

Ice breaker ships: They are used for cutting ice deposits in extremely cold climate conditions to make waters navigational. 

9. Dredgers:

Dredging is an excavation activity usually carried underwater with the purpose of gathering up bottom sediments and widening. 

Dredgers are vessels with excavation tools used for removing sand and other types of deposits from the seabed.

Dredgers are used for several purposes such as making shallow coastal areas navigational, deep-sea mining, etc.