Ordinary Seaman (OS) Jobs
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- Able Seaman (AB)1 vacancy
- Bosun (Boatswain)1 vacancy
About the role
An Ordinary Seaman (OS) is an entry-level deck rating on a seagoing ship. The OS works in the deck department, assisting the Bosun and Able Seamen with routine deck maintenance and cargo operations. During navigational watches, the OS stands lookout, steers under helm orders and learns watchkeeping duties from the Officer of the Watch. The OS does not supervise other ratings. Typical ships include general cargo ships, bulk carriers, container ships, tankers and Ro-Ro ships. The OS certificate covers ratings forming part of a navigational watch on ships of 500 gross tonnage or more. The main path is to gain sea service and move to Able Seaman (AB).
Duties on board
- Stand lookout on the bridge as directed by the Officer of the Watch.
- Steer the ship under helm orders when the Master or Officer of the Watch directs.
- Assist with mooring, unmooring and anchoring operations, handling lines and wires.
- Chip, scrape, clean and paint deck surfaces and deck fittings.
- Wash down the main deck, hatches and superstructure areas.
- Assist deck ratings and Bosun with routine deck maintenance and repairs.
- Help open and close hatch covers, and secure cargo gear as instructed.
- Pass tools and materials to the Bosun and Able Seamen during deck work.
- Keep deck stores, lockers and paint rooms clean and tidy.
- Report defects or unsafe conditions to the Bosun or Officer of the Watch.
Requirements
| Document | Convention | Note |
|---|---|---|
| Certificate of Proficiency for Rating Forming Part of a Navigational Watch | STCW II/4 | Every rating forming part of a navigational watch on a seagoing ship of 500 gross tonnage or more must be certificated. |
| Basic Safety Training (BST) | STCW VI/1 | Seafarers must receive safety familiarization and basic training or instruction in line with section A-VI/1 of the STCW Code. |
Sea service
OS certification under STCW II/4 requires approved seagoing service: not less than six months of training and experience, or special training with not less than two months of approved seagoing service. The service must be connected with navigational watchkeeping under direct supervision of the master, the officer of the watch or a qualified rating.
Medical fitness
Before beginning work on a ship, an Ordinary Seaman must hold a valid medical certificate. The certificate states that hearing and sight, and colour vision where relevant to the work, are satisfactory. A medical certificate is valid for a maximum of two years, or one year if the seafarer is under the age of 18.
Documents
- Passport
- Seaman's book (CDC)
- Certificate of Proficiency (Rating Forming Part of a Navigational Watch, STCW II/4)
- Basic Safety Training certificate (STCW VI/1)
- Valid medical certificate
- Visas when the voyage needs them
Career path
Next step: Able Seaman (AB)
Ordinary Seaman (OS): questions and answers
What does an Ordinary Seaman do on board?
An OS stands lookout, steers under helm orders, and assists with mooring and deck maintenance. The OS works under the Bosun for day work and under the Officer of the Watch during navigational watches. The OS learns watchkeeping and deck skills to progress to Able Seaman.
What certificate do I need to work as an OS?
You need a Certificate of Proficiency for Rating Forming Part of a Navigational Watch (STCW II/4) and Basic Safety Training (STCW VI/1). On seagoing ships of 500 gross tonnage or more, this certification is required.
How much sea service is needed for the OS certificate?
STCW II/4 requires approved seagoing service of not less than six months of training and experience, or special training with not less than two months of approved seagoing service. The service must be connected with navigational watchkeeping under direct supervision of the master, officer of the watch or a qualified rating.
How does an OS become an AB?
After gaining the OS certificate, you need approved seagoing service in the deck department of not less than 18 months, or not less than 12 months together with approved training, then meet the AB standard of competence under STCW II/5.
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Sources
- ILO, Maritime Labour Convention, 2006 (MLC, 2006)
- IMO, STCW/CONF.2/33 (1 July 2010), Resolution 1: The Manila Amendments to the annex to the STCW Convention
Checked against the official texts on 26 Oct 2026.