Table of Contents
Introduction
If you’re pursuing a career in the merchant navy whether in deck, engine, or technical roles you’ll hear sea time mentioned again and again. It’s not just a buzzword; it’s one of the core building blocks of your career advancement.
In this article, we’ll cover:
- What sea time means (and what it doesn’t)
- Why sea time matters (for exams, promotions, certifications)
- How sea time is calculated
- What a sea time certificate should include
- Different sea time requirements for various ranks
- Some tips & cautions
Once this is clear, you’ll understand how your time at sea is more than just experience—it’s currency.
What Exactly Is Sea Time?
The term sea time refers to the period a seafarer spends working on a ship in service—i.e. while the ship is actively engaged in voyages, not just idle at port. It counts toward the required experience you need to take certain exams or get certifications.
In other words, not every hour aboard a ship counts; what matters is your qualifying sea service. That usually means:
- You are signed on the ship, as a seafarer, under a valid contract
- The ship is operational (voyaging, transporting cargo or passengers)
- You perform your duties (watchkeeping, engine tasks, operations)
- The period is recorded officially via a sea time certificate from the master or department head.
So sea time is the documented record of your active service at sea, used to validate your experience.
Why Sea Time Is Important
Sea time isn’t just “hours under your belt.” It’s fundamental for:
- Certification / Certificate of Competency (CoC) exams
You often cannot sit for certain exams unless you’ve accumulated a minimum sea time. For example, for certs as deck or engineering officers, the STCW and DG Shipping rules demand specific sea service duration. - Promotions & Rank Advancement
Shipping companies use sea time as one of the metrics in their “matrix systems” for promotions. You may need a specified sea service in particular positions (e.g. as Second Engineer) before becoming eligible for higher rank. - Credibility When Switching Ships / Companies
When you move between companies, your sea time certificates act like a resume a proof of real experience. - Course / Training Eligibility
Some advanced or specialized courses (e.g. advanced firefighting, tankers) require prior sea time before enrollment.
In short: without sea time, your hands might remain tied even if you pass exams or have good technical knowledge.
How Is Sea Time Calculated?
Sea time calculation has rules; it’s not just about signing on and signing off. Here’s how it generally works:
Start and End Dates
- Your sea time begins on the date when the ship’s master stamps your joining (sign-on) in your documents.
- It ends on your sign-off date.
- If you stay aboard beyond contract (for valid reasons), those days may still count.
Counting in Days, Months, or Years
- Some authorities count by days; others by months.
- Often, a “month” is standardized to 30 days and a “year” as 360 days for calculation ease.
- If a voyage is partly in dry dock or ship laid up, those days may or may not count depending on rules. Many rules permit up to 2 months of dry dock time counting, but not more.
What Kinds of Time Count
Valid sea time typically includes:
- Watchkeeping duties
- Engine-room operations
- Maintenance, systems work
- Hours in evenings, nights, if you were assigned duties
- Time aboard while ship is trading (voyaging)
What usually does not count:
- Time at port doing nothing
- Long lay-ups beyond allowed threshold
- Idle or non-operational days (unless rules permit)
Example of Different Vessel Types
Sea time from non-trading vessels (like dredgers, offshore vessels) may count at reduced rates or under special conditions, depending on rules.
Also, if part of sea time is on coastal/inland voyages, authorities may only count a fraction of it or require a minimum number of days on trading ocean voyages.
Converting Mixed Sea Time
If your sea time includes various vessel types (coastal, offshore, non-trading), the qualifying sea time formula may adjust hours. For example, some days may be accepted at two thirds or half rate if the ship is non-trading.
What Should a Sea Time Certificate Include?
A sea time certificate is like your proof of experience. It must be correctly completed to be accepted by exam boards, authorities, or companies. Essential items in a certificate include:
- Name & official number of the ship
- Dates: sign-on and sign-off
- Duration of service (total days / months)
- Gross tonnage (GT) of the ship
- Engine type & specification (e.g. main engine power)
- Your rank / duties onboard (watchkeeping role, department)
- Watchkeeping details, assigned tasks
- Remarks on your conduct and performance
- Master’s signature and ship’s official seal
- Whether part of service was on coastal, inland, or other voyages
- Name of the seafarer, signature, designation
Without proper details, the certificate may be rejected.
You should secure these certificates from the department head before signing off or at least at the time of sign off—don’t wait.
Below is an example of a sea service certificate:
Sea Time Requirements by Rank / Certification
Sea time requirements differ depending on which certificate or rank you’re aiming for. Here are some typical ones (especially in Indian / DG Shipping / STCW context).
Also Read: Understanding DG Shipping’s 3-Tier Modular Course System: A Complete Guide
Checkout the below table for understanding the assessment of sea service performed in non-trading vessels operating in foreign/Indian coastal waters towards 2nd mate certification:
| Sr. No. | Course | Approved Sea-going service required for 2nd Mate FG examination | Conditions to be met if the sea-going service includes Non-trading ships |
| 1 | B.Sc in Nautical Science | 12 months | Minimum of 6 months must be performed on trading vessels |
| 2 | B.Sc. Polyvalent course | 18 months (12 months on deck + 6 months in E/R) | Minimum of 9 months must be performed on trading vessels |
| 3 | Diploma in Nautical science | 18 months | Minimum of 9 months must be performed on trading vessels |
| 4 | Science/ Engg. graduate entry scheme | 15 months | Minimum of 7.5 months must be performed on trading vessels |
| 5 | GP Rating | 36 months or 24 months | Minimum of 18 months (12 months with SSTP) must be performed on trading vessels |
| 6 | Other Deck cadets | 36 months or 24 months | Minimum of 18 months (12 months with DLP) must be performed on trading vessels |
Calculation of Qualifying Sea-going service for Second Mate (FG) certification if the service includes Non-trading ships
| Ship Type | Size | Rate of calculation for sea time assessment | For Illustration:Actual Sea service performed | Qualifying Sea going Service |
| Foreign going trading ships | 500 GT or more | Full Rate(META Manual Section M-II/11) | 12 months | 12 months |
| Trading Ships engaged on near coastal voyages of 500 miles or more | 500 GT or more | Full Rate(META Manual Section M-II/11) | 12 months | 12 months |
| Trading Ships engaged on near coastal voyages of less than 500 miles | 500 GT or more | 2/3 rd Rate(META Manual Section M-II/11) | 9 months | 9 x 2/3 = 6 months |
| Non-Trading vessels like OSV’s, Cable laying ships, AHTS, Dredgers, Diving Vessels, Survey vessels, SPS ships etc, operating in foreign waters | 3000 GT or more | First six months at full rate and further service at 2/3rd rate | 9 months | 6 + 3 x 2/3 = (6 + 2)= 8 months |
| Non-Trading vessels like OSV’s, Cable laying ships, AHTS, Dredgers, Diving Vessels, Survey vessels, SPS ships etc, operating in foreign waters | 500 GT or more but less than 3000 GT | First six months at 2/3rd rate and further service at half (1/2) rate. | 9 months | 6 x 2/3 + 3 x 1/2 = (4 + 1.5) = 5.5 months |
| Non-Trading vessels like OSV’s, Cable laying ships, AHTS, Dredgers, Diving Vessels, Survey vessels, SPS ships etc, operating in Indian coastal waters | 3000 GT or more | Maximum of four months at 2/3rd rate | 6 months | 6 x 2/3 = 4 months |
| Non-Trading vessels like OSV’s, Cable laying ships, AHTS, Dredgers, Diving Vessels, Survey vessels, SPS ships etc, operating in Indian coastal waters | 500 GT or more but less than 3000 GT | Maximum of four months at half (½) rate | 8 months | 8 x 1/2 = 4 months |
These requirements vary by country and certification authority, but the theme is consistent: higher rank demands more sea time and specialized service.
So if your goal is to become Chief Engineer, you must plan years ahead.
Common Pitfalls & Mistakes
- Delaying certification of sea time: If you forget to get your certificate signed and sealed, you may lose that period.
- Inadequate detail: Missing ship tonnage, duties, or official signatures may lead to rejection.
- Relying too much on non-voyage days: Don’t assume all days aboard will count—if the ship is idle, lay-up, or non-operational, those days may be excluded.
- Mixing vessel types without clarity: Using offshore / non-trading sea time without adjusting as per rules often leads to problems.
- Failure to maintain collection: Sea time certificates must be preserved—they’re essential credentials.
- Switching companies without handovers: Ensure certificates follow you when you move ships or employers.
Practical Tips to Maximize Valid Sea Time
- Always request your sea time certificate before signing off.
- Ensure all required fields are filled and sealed.
- Choose ships and voyages that maximize qualifying time (trading, long voyages).
- Keep copies and backups (digital scan) of certificates.
- Serve in roles that allow you the required watchkeeping / engineering duty hours.
- Avoid idle or inactive periods that may not count.
When mixing coastal / inland / non-trading services, check the rules for conversion rates.
