Merchant Marine Ranks: A Complete Guide to Hierarchy and Roles at Sea

Author : Salim Yousaf | Published On : 10 Oct 2025

The Merchant Marine is the lifeline of international trade, transporting goods and passengers across oceans and connecting economies worldwide. While most people recognize the glamour and adventure of life at sea, fewer understand the complex hierarchy that keeps a merchant ship running smoothly and safely. The ranks within the Merchant Marine are organized to ensure efficiency, safety, and accountability — every individual, from the captain to the deckhand, plays a vital role in the vessel’s operation.

In this detailed guide, we’ll explore the various Merchant Marine ranks, their responsibilities, and how the chain of command functions on board a commercial ship.

Understanding the Structure of the Merchant Marine

Merchant ships are generally divided into three main departments:

Deck Department
Engine Department
Catering (or Steward) Department

Each department has its own hierarchy and clearly defined duties. The captain or master is the overall in-charge of the vessel, but every department is managed by officers and crew who specialize in specific areas.

1. The Deck Department

The deck department is primarily responsible for navigation, cargo operations, maintenance of the ship’s exterior, and overall safety on board. This department ensures that the vessel sails safely and efficiently from one port to another.

a. Captain (Master)

The Captain, also known as the Master, is the highest-ranking officer on a merchant ship. They hold ultimate authority and responsibility for everything that happens on board, including crew management, navigation, cargo safety, and compliance with international maritime laws.
The captain also represents the ship in all official matters and ensures that every department performs its duties efficiently. In emergencies, the captain’s decisions are final and binding.

b. Chief Officer (Chief Mate)

Directly below the captain is the Chief Officer, also called the Chief Mate. This officer is the head of the deck department and is responsible for overseeing cargo loading and unloading, ensuring the ship’s stability, and maintaining safety equipment. The chief officer also supervises deck crew activities and takes charge of navigation when on watch duty.
In short, the Chief Officer is second-in-command and acts as the captain’s deputy.

c. Second Officer (Second Mate)

The Second Officer is mainly responsible for the ship’s navigation and chart corrections. They plan the voyage, maintain navigational instruments such as radar, GPS, and charts, and often handle medical duties on smaller ships. The Second Mate’s watchkeeping duties usually cover the 12:00–4:00 shifts (both AM and PM).

d. Third Officer (Third Mate)

The Third Officer is the most junior of the deck officers and is typically responsible for maintaining safety equipment, life rafts, and firefighting apparatus. They also perform navigational watch duties and assist senior officers in cargo and administrative work.

e. Deck Cadet (Trainee Officer)

A Deck Cadet is a trainee undergoing practical sea training before earning a license as an officer. They assist officers in daily operations, learn navigation, cargo handling, and ship maintenance tasks. It’s the first step in a seafarer’s officer career.

f. Bosun (Boatswain)

The Bosun is the senior-most rating in the deck department. They supervise the deck crew, such as Able Seamen and Ordinary Seamen, ensuring that all deck maintenance, mooring, and cargo operations are performed safely and efficiently.

g. Able Seaman (AB)

An Able Seaman is an experienced deck crew member who performs manual work like painting, cleaning, mooring, and steering the ship when required. ABs are skilled workers who play a vital role in maintaining the ship’s condition and assisting during navigation and emergencies.

h. Ordinary Seaman (OS)

The Ordinary Seaman is the entry-level position in the deck department. OS assists ABs and officers, performs general maintenance, and gains experience before promotion to Able Seaman.

2. The Engine Department

The Engine Department ensures that the ship’s engines, machinery, and all technical systems function properly. Without this department, no ship can move or produce power.

a. Chief Engineer

The Chief Engineer is the head of the engine department and is responsible for the operation and maintenance of all mechanical systems onboard. This includes propulsion, power generation, pumps, air conditioning, and more. The Chief Engineer reports directly to the Captain but independently manages all engine-related matters.

b. Second Engineer

The Second Engineer acts as the deputy to the Chief Engineer. They oversee daily engine operations and maintenance routines, manage fuel and lubrication systems, and ensure machinery runs efficiently. The Second Engineer often supervises the entire engine room during watch hours.

c. Third Engineer

The Third Engineer is responsible for specific machinery systems such as boilers, fuel systems, and auxiliary engines. They maintain logbooks, conduct inspections, and assist senior engineers during repairs.

d. Fourth Engineer

The Fourth Engineer handles minor machinery, including freshwater generators, air compressors, and sewage systems. They often act as the first line of defense in troubleshooting mechanical problems.

e. Engine Cadet (Trainee Engineer)

An Engine Cadet is a trainee undergoing sea service to gain practical experience. They assist engineers, learn about the ship’s machinery, and perform minor maintenance tasks under supervision.

f. Motorman / Fitter / Oiler / Wiper

These are skilled ratings who maintain machinery under the guidance of officers.

Motorman/Fitter: Repairs and maintains mechanical components.
Oiler: Lubricates moving parts of engines.
Wiper: The most junior engine room rating, responsible for cleaning and assisting with basic maintenance tasks.

3. The Catering or Steward Department

The Catering Department ensures the wellbeing and comfort of everyone onboard. Their duties include preparing meals, maintaining cleanliness, and managing provisions.

a. Chief Cook

The Chief Cook manages the galley (ship’s kitchen), plans menus, and ensures nutritious meals are prepared. They maintain hygiene standards and manage food supplies.

b. Steward / Messman

The Steward or Messman assists the cook, serves food, cleans mess areas, and maintains crew accommodation spaces. Though not involved in ship navigation or engineering, their contribution greatly affects the morale of the crew.

4. Chain of Command on a Merchant Ship

The chain of command is crucial for order and discipline onboard. It flows as follows:

Captain (Master)
↓
Chief Officer / Chief Engineer
↓
Second & Third Officers / Second, Third & Fourth Engineers
↓
Cadets & Ratings (AB, OS, Oiler, Wiper, Steward, etc.)

This hierarchy ensures that each task is performed under proper supervision and that accountability is maintained in every department.

5. Importance of Ranks in the Merchant Marine

The rank system in the Merchant Marine is more than just a hierarchy—it’s a framework for safety, efficiency, and teamwork. Each rank has defined responsibilities that contribute to the smooth functioning of the vessel. Whether it’s the captain navigating through stormy seas or a wiper keeping machinery clean, every role is essential to maritime success.

Moreover, this structured hierarchy also helps young seafarers understand their career path clearly. With experience, training, and certification, one can progress from a cadet to the highest ranks aboard.

Conclusion

The Merchant Marine operates through discipline, teamwork, and expertise, all sustained by its well-organized rank structure. Every department — deck, engine, and catering — functions in harmony to ensure that ships sail safely across the world’s oceans.

For those aspiring to join the maritime industry, understanding these ranks offers a clear roadmap to career growth. From humble beginnings as a cadet or seaman, a dedicated individual can rise to the prestigious positions of Chief Engineer or Captain. The sea rewards those who combine skill, hard work, and leadership — and the ranks of the Merchant Marine stand as a testament to that enduring spirit.