What MARPOL Is — and What It Is Not
MAROL is an IMO Convention. In UK law it is given effect through the Merchant Shipping Act 1995 and associated Statutory Instruments. MSN 1858 sets out certification and manning requirements for UK vessels; the operative pollution prevention standards come from MARPOL itself and its Annexes. The Annexes are the operative parts — know which Annex governs which substance, because an examiner will test exactly this.
| Annex | Substance | Key instrument for yachts |
|---|---|---|
| I | Oil | IOPP Certificate, Oil Record Book Part I |
| II | Noxious liquid substances in bulk | Unlikely to apply to yachts |
| IV | Sewage | Rarely certificated for yachts; Special Areas emerging |
| V | Garbage | Garbage Management Plan, Garbage Record Book |
| VI | Air emissions (SOx, NOx, GHGs) | Fuel oil, BDN, MARPOL sample |
Annex III (packaged harmful substances) exists but is not examined in depth at this level.
Special Areas vs Normal Sea Areas — The Core Distinction
A Special Area under MARPOL has stricter discharge prohibitions than the open sea because of its enclosed nature, heavy traffic, or ecological sensitivity. The designation is Annex-specific: a sea can be a Special Area under one Annex and not another. Examiners probe this directly.
- Mediterranean Sea: Special Area under Annex I (oil) and Annex V (garbage) — not Annex IV.
- Red Sea: Special Area under Annex V from 1 January 2025.
- Antarctic Area: Total prohibition under Annex I — no overboard discharge of oil whatsoever, regardless of treatment.
- Baltic, North Sea, Caribbean and others each carry their own Annex-specific restrictions — know the principle, then verify the specific Annex for any area you are trading.
Annex I — Oil: Who Must Do What
Yachts under 400 GT cannot legally discharge oily bilge water at sea; they must retain it for port reception facilities (Reg 15.6). The 15 ppm filtered-discharge route (Reg 15) is only available to ships 400 GT and above equipped with approved filtering equipment (Reg 14). The Oil Record Book Part I is carried by vessels 400 GT and above; the IOPP Certificate is required for vessels 400 GT and above on international voyages, on a 5-year survey cycle.
Annex V — Garbage: Who Must Do What
The general rule is no discharge of garbage into the sea unless specifically permitted (food waste in certain conditions, for example). The Garbage Management Plan (GMP) and Garbage Record Book (GRB) are required for vessels 100 GT and above or those certified to carry 15 or more persons. The 100 GT threshold replaced the previous 400 GT threshold on 1 May 2024. GRB entries are retained for 2 years from the date of the entry.
Annex VI — Air Emissions: Fuel and Documentation
Global sulphur cap: 0.50% (in force since 2020). In a Sulphur Emission Control Area (SECA): 0.10%. The Mediterranean became a SECA on 1 May 2025 — a critical date for any yacht on Mediterranean routes.
Bunker Delivery Notes (BDNs) must be retained for 3 years from delivery. The MARPOL representative fuel sample must be retained until the fuel is substantially consumed and for a minimum of 12 months.
Minimum flash point for fuel oil in use (SOLAS II-2 Reg 4): 60 °C. Emergency generator fuel: 43 °C minimum.