This post is a little different from what I usually post about. I decided to write it since people that are not involved with the merchant navy often ask me about the differences between all the ships they see. So I’ll talk about those I think are more relevant.
There are several types of ships according to their function:

Container ships:
This type of ships appeared with the generalization of containers, where the cargo is placed inside containers, which are placed on the decks of this ships. This technique allows companies to save time and space on board, and therefore save money, since the port’s container crane only needs to lift the containers from the trucks and load them on the ship, instead of workers having to load everything by hand. This idea came from a truck driver, Malcom P. McLean, who was tired of waiting for his cargo to be unloaded off of his truck, and thought it would be amazing if they could just load the entire back of his truck onto the ship.

Dry Bulk Carriers:
This ships transport their cargo in bulk, in their cargo holds. To make this profitable, the cargo is transported in large quantities and consists mainly of corn, cereal, grains, minerals, etc… Right now there are at least three ships experimenting with kite-like sails as auxiliary propulsion in order to reduce carbon dioxide emissions. This method allows for a reduction up to 30% of said emissions.


Tankers, which include:
Chemical tankers:
Chemical tankers have the most advanced technology on the market, in comparison to others, due to the sensitive nature of the transported products. This ships transport all kinds of chemical products in liquid state inside their tanks like petrochemicals, coal and tar products, carbohydrate derivatives, vegetable or animal oils, heavy chemicals, etc…
They are divided in three groups according to the security level of the products they carry:
• Type I ship – dangerous substances with severe effects beyond ship vicinity;
• Type II ship– dangerous substances with severe effects in the ship vicinity;
• Type III ship– Dangerous substance with less negative impact on the environment.

Oil tankers:
They transport oil, both as crude oil and as its by-products, such as gasoline and diesel.


LNG ships:
This ships transport liquefied natural gas. They are easily identified due to the spherical tanks on the main deck.

General cargo ships:
As the name suggests, they transport all kinds of cargo. They lost much of their market share when container ships started gaining popularity.

Ferry boats:
Also known as Ro-ro (Roll-on/roll-off), tis are ships in which the cargo gets on and off by themselves, such as vehicles and people. They can, for example, cross rivers with vehicles and passengers, or carry them between countries with commercial intent.
There are 13 types of ferry boats, including but not limited to: hovercraft ferries, ro-ro ferries, catamaran ferries, cruise ferries, foot ferry (which only transports passengers on foot), train ferry (which transports railway vehicles), etc…

There are also ships designed to support other ships, such as:

They can help other ships in many ways, by helping them getting in difficult areas, towing, putting out fires, break ice, etc…
Curiosity: The Edward J Moran, one of the biggest and most powerful tugboats in the world, can reach a 14 knots speed, and is capable of generating a 6500 horse-power force when towing, more than double of what average tugboats are capable of.

Passenger ships:

Cruise ship:
This passenger ships has leisure as the purpose of the trip. There are lots of things to do while on board and, depending on the ship, it can even feel like you are in floating city.
The biggest cruise ship nowadays is the Harmony of the Seas, with an overall length of 362 meters (the Eiffel tower has 300 meters) and is 70 meters tall, which is equivalent to 16 floor building.

Sailing ships:
A sail ship is a ship that moves with the wind power gathered by the sails. Nowadays, they are mostly used for leisure and tourism.



Fishing vessels:

They can be anything from small rowboats for rudimentary fishing to large industrial ships with high-tech for large fishing operations.
Due to the different nature of their operation, they have different and specific sets of rules as far as security and crew obligations go.