01
What it is
Maritime OSINT is the practice of tracking vessels, tracing ownership, and documenting incidents using publicly accessible data, without access to classified or proprietary systems. It covers the full investigative arc from AIS position data through corporate registry research, port inspection records, casualty documentation, and sanctions screening.
When a vessel goes dark in a conflict zone, the AIS gap is not the end of the investigation. It is the beginning. In June 2026, the Ever Lovely transmitted an AIS heading field inconsistent with its stated course in the Strait of Hormuz. Cross-referencing that signal against independent AIS reception and satellite positioning placed the vessel in a coercion corridor before the drone strike was reported. The open record did not prove what happened. It proved what could not have happened, and that is what made it publishable. This guide covers that methodology: from establishing vessel identity through AIS tracking, ownership tracing, port inspection records, incident reconstruction, and sanctions screening.
When to use this guide
- Tracking a vessel's movements near a conflict zone, sanctioned port, or area of investigative interest.
- Verifying official accounts of a maritime incident against the navigational record.
- Tracing the beneficial owner behind a flag-of-convenience vessel or opaque corporate structure.
- Identifying AIS gaps or spoofing patterns that indicate potential sanctions evasion.
- Documenting ship-to-ship transfers linked to sanctioned cargo or illicit trade networks.
02
How to track and investigate a vessel using open sources
The complete workflow: from establishing vessel identity through AIS tracking, ownership tracing, port inspection records, incident reconstruction, and sanctions screening.
The following tools cover the full maritime OSINT workflow. Free tools are listed before paid.
MarineTraffic: Real-time AIS position data and historical voyage playback. Free tier available; extended history and satellite AIS require a paid subscription.
VesselFinder: Independent AIS source for cross-referencing MarineTraffic data. Free tier available. Use alongside MarineTraffic and flag any positional discrepancies.
Equasis: Multi-administration maritime safety registry founded by European maritime administrations, with IMO holding observer status. Links vessels to registered owner, ship manager, flag state, class society, and port state control inspection history. Free with registration.
Global Fishing Watch: Independent AIS reception and gap detection. Free. Particularly useful for identifying dark vessel periods and cross-referencing gaps against MarineTraffic.
OpenCorporates: Corporate registry search for tracing ownership chains across jurisdictions. Free and paid tiers.
ICIJ Offshore Leaks: Searches the Panama Papers, Paradise Papers, Pandora Papers, and related leaked datasets by company and individual name. Free.
OpenSanctions: Cross-references individuals and entities against multiple international sanctions regimes simultaneously. Free.
TankerTrackers: Specialist ship-to-ship transfer tracking with satellite imagery integration. Paid. Relevant for sanctions evasion investigations involving crude oil and petroleum products.
Before you begin
Anchor on the IMO number, not the vessel name
Vessel names change. Flags change. Ownership changes. The IMO number does not. It is a permanent seven-digit identifier assigned at build. Retrieve it from MarineTraffic or Equasis before doing anything else. Every subsequent query in this workflow should be anchored to the IMO number.
Legal considerations
All techniques in this guide use publicly accessible data. Do not interact with vessel systems or attempt to access non-public maritime databases. Sanctions research involving designated individuals or entities may carry legal implications depending on your jurisdiction; consult counsel before publishing findings that identify sanctioned persons.
Two cards in this series support the workflow above but aren't linked in the steps: MAR-001 for the full AIS and MMSI vessel tracking methodology, and MAR-002 for reading Equasis ownership records line by line.
