Third Officer Duties and Responsibilities: The Ultimate Guide

by | Last updated Nov 24, 2023 | Career Guide, Shipboard Ranks | 0 comments

A Third Officer is a crucial member of the deck department on board merchant vessels. As a licensed mariner, his duties and responsibilities are extensive and critical to the safety and efficiency of the vessel’s operations.

The fundamental aspect of his job is maintaining the safety and fire-fighting equipment. However, his duties extend far beyond this core responsibility.

In this ultimate guide, we’ll break down the job description of a Third Mate that even a newbie can understand.

 I was once a cadet myself when I first learned about this position, so I understand the need for clear, straightforward explanations.

What is a Third Officer?

A Third Officer or Third mate is a licensed member of the deck department who reports directly to the Chief Officer and the Master. You will also likely know him on board as 3/M, 3/O, 3/Off., 3rd Off., 3rd Mate, or Tercero Opisyal.

Like the Chief Mate and the Second Mate, he is also a watchkeeper on the bridge during navigation and inside the Cargo Control Room during cargo operations.

He also assists the Captain in preparing essential paperwork, including drills, port documents, extra allotments, inventories, and reports. Sometimes, he’s also in charge of the vessel’s slop chest.

Duties and Responsibilities

The duties of a Third Officer can vary depending on the type of vessel they are working on and the size of the deck department. But the fundamentals remain the same.

Here are the core duties and responsibilities typically associated with this role.

Navigation/ Bridge Works

  1. Keep the 0800/1200 & 2000/2400 bridge watch.
  2. Navigate the ship safely, following COLREGS and company regulations.
  3. Chart the ship’s position according to the voyage plan.
  4. Familiarize yourself with the Bridge Standing Orders.
  5. Use all the equipment on the bridge properly.
  6. Be professional when using and calling through the VHF radios.
  7. Keep the Admiralty List of Lights and Fog Signals corrected and up to date.
  8. May assist with the correction of Radio Signals as per the Second Mate’s advice.
  9. Write appropriate entries in the official deck log book.
An official deck log book of a merchant ship.
  1. Follow Master’s Night Order Book.
  2. Solve for compass error, gyro error, and position fixing using the sextant if the voyage allows.
  3. Ensure that day shapes required by COLREGS are maintained in good condition.
  4. Test the general alarm signal and the ship’s whistle at noon daily when appropriate.
  5. Test bridge equipment in cooperation with the Second Officer.
  6. Carry out departure/ arrival testing procedures.
  7. Use the Bridge Safety Checklist whenever appropriate.
  8. Assist the Master on the bridge during maneuvering. But he can also be assigned on deck during mooring operations, depending on the Master’s discretion.

Shipboard Safety

  1. Maintain all life-saving appliances (lifeboats, lifejackets, liferafts, lifebuoys, pyrotechnics, floats, etc.) and associated equipment to a high standard.
  2. Ensure that all fire fighting equipment (extinguishers, hoses, nozzles, fireman’s outfit, BA, etc.) is in good working order through inspection, testing, and maintenance.
  3. Responsible for the upkeep of the flags (country flags and pennants).
  4. Advise the Chief Office whenever a specific safety equipment requires maintenance beyond his capabilities.
  5. Ensure all emergency food, water, first aid kits, and pyrotechnics (bridge & lifeboats) are renewed.
  6. Conduct a fire safety watch inside the accommodation at night after the watch.
  7. Familiarize newcomers with life-saving and fire-fighting equipment.
  8. Ensure that all LSA and FFE have the correct and updated inspection tags.
  9. Verify that all signs and posters are in excellent condition and correctly displayed throughout the vessel.
  10. Ensure all fire extinguishers are clearly marked to indicate the type.
  11. Verify that appropriate operating instructions are made out in English AND the second primary language of the ship.
  12. Ensure adequate spares of all LSA and fire fighting equipment are kept aboard.
  13. Update the muster list, emergency instructions, station bill cards, crew list, and telephone numbers on board.
  14. Ensure that all fire plans are updated and posted correctly on selected parts of the ship.
  15. Encourage the crew to perform Videotel and computer-based training (CBT).
A question from the ship's Computer-based Training or CBT.

Reports and Record-Keeping

  1. Create orders and requisitions necessary for safety and fire fighting equipment.
  2. Maintain records of expiry dates of equipment.
  3. Create records and reports of safety drills and training in the appropriate log book.
  4. Keep records of any maintenance or inspection, as necessary.
  5. Prepare extra allotments for the crew to fill out.
  6. Save the printed reports in a specified folder for future reference.
  7. Prepare port documents as instructed by the Master.
  8. Maintain records and minutes of safety committee meetings.
  9. Prepare near-miss reports every month.
A Near Miss report  and logs for the month of October 2012.

Cargo Operations

  1. Assist the Chief Officer with supervising and organizing cargo operations while the vessel is in port.
  2. Take an hourly rate of loading/ discharging progress.
  3. Prepare his own loading/discharging plan for training purposes, which will be checked and compared to the Chief Officer’s plan.
  4. Attend to the proper hoisting/lowering of flags while in port.
  5. Keep a record of important occurrences during his watch.
  6. Check the vessel’s draft as per the Chief Mate’s advice.
  7. Perform ballasting and deballasting operations.
  8. Assist the Chief Officer with paperwork when the agent, loading masters, surveyors, or authorities arrive.
  9. Familiarise with the cargo plan.
  10. Assist the Chief Officer during ullaging or tank inspection.
  11. Ensure that scuppers are plugged and fire wires and mooring wires are attended.
  12. Follow the Chief Officer’s and Master’s standing orders to in-port operations.
A ship de-ballasting while alongside a terminal.
Deballasting while alongside.

Duties in Case of Emergencies

  1. Fire on board – Squad Leader.
  2. Abandon Ship – Bring EPIRB, SART, and emergency VHF radios.
  3. Man Overboard – Boatman.
  4. Other emergencies – Refer to the Shipboard Emergency Manual or the Vessel’s Response Plan (VRP).


  1. Read, familiarize, and comply with all procedures/instructions manuals of the Company’s Management System, which relate to his duties and responsibilities.
  2. Train deck cadets as per the Chief Mate’s advice.
  3. Prepare Handover Notes for the reliever and briefly familiarize him with your duties upon his arrival on board.

The third officer’s duties and responsibilities listed here are not exhaustive. 

Like on any other ship, the Master, at his discretion, may assign additional duties for the safe and smooth operation of the vessel.

Sometimes, he may even assist the Chief Officer in the upkeep and inventory of the infirmary, medical chest, and the hospital.

His role may also change depending on the company policy, so it is better to consult with the company’s procedure manual first or the outgoing Third mate.

May the winds be in your favor.



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