Underwater operations
Divers or remotely operated vehicles are working below a vessel that cannot easily move out of the way.
"UNDERWATER OPERATIONS IN PROGRESS BY M/V …" covers diving, remotely operated vehicle (ROV) work, pipeline and cable inspection and construction on the seabed. The vessel is connected to divers or equipment and is restricted in its ability to manoeuvre, so the warning asks others to keep clear, often by a stated distance.
Under the Collision Regulations such a vessel shows the ball-diamond-ball day shape or the equivalent lights, and small craft supporting divers fly the International Code flag A. Many of these warnings run until further notice and name the vessel involved.
What the archive shows
5,904 messages in this archive use “Underwater operations”, the earliest issued 1991-04-11 and the latest 2026-09-22. 18 of them are in force in the latest lists we collected. A hazard reported again and again counts once per message.
The largest yearly count is 2001, with 642 messages. Collection is incomplete between 2024-05 and 2026-08-17, so 2024, 2025 and 2026 are not comparable with fully collected years.
Surveys accounts for 4,667 of 5,904 recorded messages (79%), the largest warning type group in this selection.
Located messages that use it fall in 64 sea areas; the most frequent are South Atlantic Ocean (869), Celtic Sea (730) and North Sea (588).
Its use is spread fairly evenly through the year: the busiest month, June, has 567 messages and the quietest, October, 426.
By warning series: HYDROLANT 4,161, HYDROPAC 1,357, NAVAREA IV 292 and NAVAREA XII 48, and 3 more.
Messages using it, by year of issue
By month of issue, all years
Where it appears · 64 sea areas
In force now · 18
- AUSCOAST 300/26 · Surveys · Indian Ocean2026-09-22 · in force
SPECIAL PURPOSE VESSEL FUGRO KWILENA / MLOV8 / 503147420 CONDUCTING UNDERWATER OPERATIONS IN AN AREA BOUNDED BY 20-19.72 S TO 20-35.47 S AND 115-42.52 E TO 115-43.80 E 1.5NM…
Special purpose vessel fugro kwilena / MLOV8 / 503147420 conducting underwater operations in an area bounded… → - HYDROLANT 1850/26 · Surveys · South Atlantic Ocean2026-09-18 · in force
SOUTH ATLANTIC. BRAZIL. 1. UNDERWATER OPERATIONS IN PROGRESS UNTIL 250259Z SEP BY M/V SIEM PILOT IN 22-25.32S 039-56.55W. WIDE BERTH…
Underwater operations in progress until 250259Z sep by M/V siem pilot in 22-25.32S 039-56.55W → - NAVAREA IV 832/26 · Surveys · North Atlantic Ocean2026-08-27 · in force
NORTH ATLANTIC. TRINIDAD AND TOBAGO. 1. UNDERWATER OPERATIONS IN PROGRESS UNTIL 052200Z DEC BY M/V SEVEN SEAS IN 10-06.05N 060-17.51W. 500 METER BERTH…
Trinidad and tobago → - HYDROPAC 2288/26 · Surveys · Indian Ocean2026-08-10 · in force
INDIAN OCEAN. AUSTRALIA. UNDERWATER OPERATIONS IN PROGRESS UNTIL FURTHER NOTICE BY VESSEL VE CONSTRUCTOR IN AREA BOUND BY 19-12.00S…
Underwater operations in progress until further notice by vessel ve constructor in area bound by 19-12.00S… → - AUSCOAST 270/26 · Surveys · Indian Ocean2026-08-10 · in force
SPECIAL PURPOSE VESSEL VE CONSTRUCTOR / H9YT / 373335000 CONDUCTING UNDERWATER OPERATIONS IN AN AREA BOUNDED BY 19-12.00S TO 19-21.00S AND 116-30.00E TO 116-50.00E 0.5NM…
Special purpose vessel ve constructor / H9YT / 373335000 conducting underwater operations in an area bounded… → - NAVAREA IV 621/26 · Surveys · North Atlantic Ocean2026-06-24 · in force
NORTH ATLANTIC. GUYANA. 1. UNDERWATER OPERATIONS IN PROGRESS UNTIL 31 DEC BY M/V PRINSENGRACHT IN AREA BOUND BY 08-03.09N 056-46.88W,…
Underwater operations in progress until 31 dec by M/V prinsengracht in area bound by 08-03.09N 056-46.88W,… →
How it reads in recent messages
- HYDROPAC 2741/26 · Surveys · Indian Ocean2026-09-22
EASTERN INDIAN OCEAN. AUSTRALIA. 1. UNDERWATER OPERATIONS IN PROGRESS UNTIL FURTHER NOTICE BY M/V FUGRO KWILENA IN AREA BOUND BY 20-19.72S…
Underwater operations in progress until further notice by M/V fugro kwilena in area bound by 20-19.72S… → - HYDROLANT 1869/26 · Surveys · South Atlantic Ocean2026-09-21
SOUTH ATLANTIC. BRAZIL. 1. UNDERWATER OPERATIONS 0800Z TO 1800Z DAILY 22 SEP THRU 06 OCT BY M/V NORD HOUSTON AND M/V COMANDO B IN…
Underwater operations 0800Z to 1800Z daily 22 sep thru 06 oct by M/V nord houston and M/V comando b in… → - HYDROLANT 1868/26 · Surveys · South Atlantic Ocean2026-09-20
SOUTH ATLANTIC. BRAZIL. 1. UNDERWATER OPERATIONS 0800Z TO 1800Z DAILY 21 SEP THRU 05 OCT BY M/V COMANDO B AND M/V LINDSAYLOU IN 20-23.93S…
Underwater operations 0800Z to 1800Z daily 21 sep thru 05 oct by M/V comando b and M/V lindsaylou in… → - HYDROLANT 1867/26 · Surveys · South Atlantic Ocean2026-09-20
SOUTH ATLANTIC. BRAZIL. 1. UNDERWATER OPERATIONS 0800Z TO 1800Z DAILY 21 SEP THRU 05 OCT BY M/V COMANDO B AND M/V EMERALD DAISHAN IN…
Underwater operations 0800Z to 1800Z daily 21 sep thru 05 oct by M/V comando b and M/V emerald daishan in… → - HYDROLANT 1866/26 · Surveys · South Atlantic Ocean2026-09-20
SOUTH ATLANTIC. BRAZIL. 1. UNDERWATER OPERATIONS 0800Z TO 1800Z DAILY 21 SEP THRU 05 OCT BY M/V MDS ARIADNE AND M/V COMANDO B IN…
Underwater operations 0800Z to 1800Z daily 21 sep thru 05 oct by M/V mds ariadne and M/V comando b in… → - HYDROLANT 1865/26 · Surveys · South Atlantic Ocean2026-09-20
SOUTH ATLANTIC. BRAZIL. 1. UNDERWATER OPERATIONS 0800Z TO 1800Z DAILY 21 SEP THRU 05 OCT BY M/V MDS ARIADNE AND M/V COMANDO B IN…
Underwater operations 0800Z to 1800Z daily 21 sep thru 05 oct by M/V mds ariadne and M/V comando b in… →
Earliest in the archive
- NOAAORR-6801 · Spills · Ligurian Sea1991-04-11
…Tanker Owners Pollution Federation (ITOPF), volunteers, remotely operated vehicle (ROV), sub-surface oil, boom, containment boom, skimmers, suction operations, vacuum trucks,…
On april 11, 1991, the tanker haven caught fire while anchored 7 miles off of genoa, italy →
Often in the same message
Related terms
- Restricted in ability to manoeuvre
- A vessel whose work — cable laying, diving, dredging, towing — stops it from keeping out of other ships' way.
- Wide berth requested
- Keep well clear — or, when a distance is given ("TWO MILE BERTH REQUESTED"), at least that far away.
- Cable operations
- A ship is laying, burying or repairing a submarine cable, usually along a stated route.
- Until further notice
- The operation or danger has no scheduled end; the warning stays in force until a later message cancels it.
Warning types that use it
- Cable ops — Cable laying, pipeline and seismic operations.
- Structures — Platforms, wind turbines and fish farms established, under construction or removed.
Counts cover the messages in this archive that use the term, recounted 2026-09-24; see coverage for what is collected and since when. Not for navigation — follow official NAVAREA and coastal broadcasts.