Reference
Maritime Glossary
Plain-English definitions for offshore, maritime and synchronised-operations terminology — written by mariners, for anyone evaluating, procuring or operating safety-critical maritime systems.
Synchronised-Operations Modular System
SOMS
- The GreenHulls platform — a modular maritime operations system that unifies vessels, offshore installations and shoreside teams onto a single real-time visual interface with logic-driven digital workflows.
500m Safety Zone
- A regulator-defined three-dimensional exclusion zone extending 500 metres horizontally from an offshore installation. Established under the UK Petroleum Act 1987 and equivalent international frameworks (UNCLOS Article 60(5)). Unauthorised entry is an offence.
Emergency Response and Rescue Vessel
ERRV
- A vessel contracted to provide standby, search-and-rescue, fire-fighting and command-and-control support to one or more offshore installations. Required by most North Sea safety cases.
Offshore Installation Manager
OIM
- The most senior person on an offshore installation, holding statutory responsibility for the safety of the installation and everyone on it under the UK Offshore Installations and Pipeline Works (Management and Administration) Regulations.
General Activity Risk Assessment
GAR
- A dynamic risk-assessment framework used by attending vessels and installations to rate the combined risk of an operation, typically expressed as a green/amber/red status that gates whether work proceeds.
Mobile Offshore Drilling Unit
MODU
- A floating or self-elevating drilling unit (jack-up, semi-submersible, or drillship) capable of being relocated between drilling locations.
Floating Production, Storage and Offloading
FPSO
- A floating vessel that processes hydrocarbons from subsea wells, stores them onboard, and periodically offloads to shuttle tankers. Common in deep-water fields where pipeline infrastructure is uneconomic.
Dynamic Positioning
DP
- A computer-controlled system that automatically maintains a vessel's position and heading using its own thrusters and propellers, without anchoring. Classified DP1, DP2 or DP3 depending on redundancy level.
Ship-to-Ship Transfer
STS
- The transfer of cargo (typically crude oil, LNG or LPG) between two vessels positioned alongside each other at sea or at sheltered locations. Governed by OCIMF STS Transfer Guide.
Bunkering
- The process of transferring fuel oil (bunker fuel) to a vessel for its own propulsion and onboard machinery, either at port, at anchor or via a bunker barge.
Port State Control
PSC
- The inspection regime by which a state inspects foreign-flagged vessels visiting its ports to verify compliance with international maritime conventions (SOLAS, MARPOL, MLC, STCW). Failed inspections can result in detention.
Make-Safe
- A coordinated stand-off or pause instruction issued during a safety-critical operation. In SOMS, broadcast as a one-tap audible alert simultaneously to every connected asset, rather than relying on a single VHF transmission.
Pencil-whipping
- Industry slang for completing a paper checklist by signing items off without actually performing or verifying them. A recognised contributor to procedural-control failures; eliminated by logic-driven digital workflows that block out-of-order progression.
Automatic Identification System
AIS
- A VHF-based transponder system that broadcasts a vessel's identity, position, course and speed to other vessels and shore stations. Mandatory on most commercial vessels under SOLAS Chapter V.
Marine Assurance
- The discipline of independently verifying that a chartered vessel meets the safety, technical and operational standards required by the duty holder, prior to and during contract execution.
Duty Holder
- Under the UK Offshore Safety Case Regulations, the entity legally responsible for the safe operation of an offshore installation — typically the operator. Owes a defined duty of care to everyone on or around the installation.
Walk-to-Work
W2W
- A vessel-based personnel transfer method using a motion-compensated gangway, allowing technicians to walk directly from the vessel onto an offshore installation or wind turbine without lifting or swinging.
Permit to Work
PTW
- A formal written authorisation system that controls high-risk work activities by ensuring hazards are identified, controls are in place, and competent personnel have approved the work before it starts.
Simultaneous Operations
SIMOPS
- Two or more separate offshore operations being conducted in the same area at the same time (e.g. drilling and production, or cargo transfer and dive operations). Requires explicit pre-approved coordination procedures.
Crew Transfer Vessel
CTV
- A small, fast vessel — typically a catamaran — used to transfer technicians and equipment to offshore wind turbines and substations. Standard workhorse of the offshore wind O&M model.
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