Source: Christian H. on LinkedIn | OpenOceanWatch Demo
Background: AIS and Its Limitations
The Automatic Identification System (AIS) is the primary mechanism by which vessels broadcast their identity, position, course, and speed to other ships and shore-based stations [1]. Under International Maritime Organization (IMO) regulations, AIS is mandatory for all vessels over 300 gross tonnage on international voyages, all cargo ships over 500 gross tonnage, and all passenger ships regardless of size [1]. Vessels below these thresholds, including the majority of the world’s fishing fleet, are not required to carry or transmit AIS [2].
When a vessel’s AIS transponder is disabled, switched off, or simply absent, the vessel does not appear in AIS-based tracking systems such as MarineTraffic, VesselFinder, or ShipFinder [3]. These vessels are referred to in maritime intelligence and domain awareness contexts as “AIS-dark,” “dark vessels,” or “ghost ships” [2] [3]. The term “shadow fleet” refers specifically to a subset of dark vessels — primarily aging tankers — operating outside normal compliance controls to move sanctioned crude oil from Russia, Iran, and Venezuela [4].
According to Global Fishing Watch, the majority of the world’s fishing vessels do not broadcast AIS positions, and of vessels on the Illegal, Unreported, and Unregulated (IUU) vessel list, only a small fraction have transmitted AIS in recent years [2]. A review of approximately 200 vessels with documented cases of forced labor found that only about one quarter broadcast AIS [2].
OpenOceanWatch: Platform Overview
OpenOceanWatch is an open-source maritime domain awareness platform that cross-references satellite imagery with AIS data to identify vessels that appear in imagery but do not correspond to an active AIS signal [5]. The platform applies satellite data, artificial intelligence, and open maritime databases to surface discrepancies between physical vessel presence and AIS-reported presence [5].
The core detection methodology involves comparing vessel signatures detected in satellite imagery — including Synthetic Aperture Radar (SAR) and optical imagery — against concurrent AIS transmissions in the same geographic area [2] [6]. Vessels present in imagery but absent from AIS records are flagged as potential dark vessels [2].
The platform provides a publicly accessible demo interface [5].
Technical Context: Satellite-Based Dark Vessel Detection
Satellite-based dark vessel detection draws on multiple data sources:
| Data Source | Capability | Limitation |
|---|---|---|
| Sentinel-1 (SAR) | Detects vessel presence through cloud cover; estimates vessel size | Resolution of 20m; cannot determine vessel identity |
| Sentinel-2 (Optical) | Estimates vessel speed and course; 10m resolution | Cannot penetrate cloud cover |
| Commercial SAR | Higher resolution; targeted coverage | Cost-constrained; not continuous |
| VIIRS (NASA) | Nighttime vessel detection via light emissions | Limited to vessels with visible light sources |
| AIS (Terrestrial + Satellite) | Real-time position, identity, course, speed | Only covers AIS-transmitting vessels |
Sources: Global Fishing Watch [2]; Starboard Intelligence [6]; DTU Technical University of Denmark [7]
Combining SAR imagery with AIS data allows analysts to identify vessels that are physically present in a given area but not transmitting AIS. The discrepancy can result from: absence of AIS equipment (common for small fishing vessels), equipment malfunction, deliberate disabling to avoid detection, or AIS spoofing — the transmission of false position data [6] [7].
Operational Context: Shadow Fleet and Critical Infrastructure
Between 900 and 2,000 aging oil tankers are estimated to be operating in the shadow fleet as of early 2026, primarily moving sanctioned crude from Russia, Iran, and Venezuela [4]. These vessels frequently operate without standard insurance, under flags of convenience, and with obscured ownership structures [4].
The shadow fleet has been linked to incidents near critical maritime infrastructure, including subsea cables and offshore energy installations [5]. Sanctions enforcement agencies, including the U.S. Office of Foreign Assets Control (OFAC) and the EU, have designated hundreds of vessels and associated entities for shadow fleet activity [4].
OpenSanctions maintains a publicly downloadable database of sanctioned vessels updated on a rolling basis [8].
OSINT Tool Ecosystem for Maritime Domain Awareness
The following open-source tools are used by analysts for maritime domain awareness, as documented by SpecialEurasia (2026) [3]:
| Tool | Primary Function | Access Model |
|---|---|---|
| MarineTraffic | AIS-based vessel tracking, ghost vessel detection | Freemium |
| VesselFinder | AIS tracking, cross-platform verification | Freemium |
| ShipFinder | Vessel status lookup by name or IMO number | Freemium |
| Global Fishing Watch | SAR + optical satellite fusion; dark vessel mapping | Free (research) |
| OpenOceanWatch | AIS-satellite cross-reference; dark vessel flagging | Open demo |
| OpenSanctions | Sanctioned vessel database | Free download |
| HawkEye 360 | RF geolocation; AIS gap analysis | Commercial |
References
[1] International Maritime Organization. (n.d.). AIS transponders. Retrieved June 8, 2026, from https://www.imo.org/en/OurWork/Safety/Pages/AIS.aspx
[2] Global Fishing Watch. (2022). Dark vessels: Revealing all vessel traffic at sea. Retrieved June 8, 2026, from https://globalfishingwatch.org/research-project-dark-vessels/
[3] SpecialEurasia. (2026, March 31). 6 OSINT tools for maritime intelligence. Retrieved June 8, 2026, from https://www.specialeurasia.com/2026/03/31/osint-tools-maritime-intel/
[4] AML Watcher. (2026, March 4). Maritime sanctions evasion risks for FIs with the rise of dark fleet. Retrieved June 8, 2026, from https://amlwatcher.com/blog/maritime-sanctions-evasion-risks-for-fis-with-the-rise-of-dark-fleet/
[5] Christian H. (2026, June 6). [LinkedIn post on OpenOceanWatch and dark vessel detection]. LinkedIn. Retrieved June 8, 2026, from https://www.linkedin.com/posts/christian-h-315a871b5_osint-ghostships-darkvessels-share-7469081328143974400-f24R/
[6] Starboard Intelligence. (2022, November 12). Satellite dark vessel detection for maritime domain awareness. Retrieved June 8, 2026, from https://www.starboardintelligence.com/articles/satellite-dark-vessel-detection-for-maritime-domain-awareness
[7] Technical University of Denmark (DTU). (2024, September 13). Maritime surveillance: Finding dark ships with satellites and artificial intelligence [PDF]. Retrieved June 8, 2026, from https://backend.orbit.dtu.dk/ws/files/390125979/Maritime_Surveillance_Finding_Dark_Ships_with_Satellites_and_Artificial_Intelligence.pdf
[8] OpenSanctions. (2025, May 27). Targeting the shadow fleet: A new download of sanctioned vessels. Retrieved June 8, 2026, from https://www.opensanctions.org/articles/2025-05-27-maritime-download/