Eight Capsizes, Nine Deaths: What Tug Biter and Hebridean Princess Tell the Industry About Girting

Off Greenock, 24 February 2023

The tug Biter was assisting the passenger vessel Hebridean Princess off Greenock in the Clyde estuary when the towline angle increased beyond the tug’s safe working envelope. The towline generated a heeling moment the tug could not counter. Biter capsized and sank. Two crew members were killed.

The Marine Accident Investigation Branch investigated and published its report — MAIB 17/2024 — in November 2024. In February 2026, the MAIB issued Safety Bulletin SB1/2026: a safety video distilling the key lessons from the investigation for promulgation to tug crews across the UK.

This was the eighth conventional tug capsize investigated by the MAIB since 1998. Nine people have been killed across those eight accidents.

What is Girting?

Girting — also called girthing — is the specific capsize mechanism that conventional tugs face during assist and escort operations. It occurs when the towline angle increases until the transverse component of the towing force exceeds the tug’s ability to pivot fast enough to realign. The stern is pulled down toward the towline side. The working deck floods. The tug capsizes toward the direction of pull.

Conventional tugs — with a fixed tow hook amidships or aft — are most vulnerable when the towline approaches 90° to the tug’s centreline. At that angle, the entire towing force becomes a transverse heeling load. The tug cannot engine or steer its way out. The only protection is to release the towline — instantly — via the slip hook.

Escort tugs and Voith Schneider propeller tugs use different towing geometry and propulsion arrangements that either eliminate or greatly reduce girting risk. They are not subject to the same constraint. Conventional tugs are, and they remain common in UK port operations.

Eight Accidents Since 1998

The Biter/Hebridean Princess investigation was not the MAIB’s first report on conventional tug girting. It was the eighth. The accidents have occurred across different ports, different operators, and different assisted vessels. The mechanism is the same in each case. The intervention that would have prevented each capsize is the same: release the towline before the heeling moment becomes irreversible.

The MAIB’s decision to accompany its SB1/2026 bulletin with a safety video — rather than a written bulletin only — reflects a deliberate effort to reach operational tug crews in a format more accessible than a PDF. The single recommendation (S2026/122) requires six UK industry bodies to distribute the video to their members, including the British Tugowners Association, UK Chamber of Shipping, UK Harbour Masters’ Association, and the UK Maritime Pilots’ Association.

For Tug Masters and Crews

Know your slip hook. Where is it? Can you reach it from a safe position when the tug is heeling? Can you operate it alone, without tools, under load? If you’re not certain of the answers, that’s a training gap to close before the next assist job.

Know your towline angle. The risk zone begins well before 90°. MGN 471(M+F) sets out the safe working envelope for conventional tug-assist operations. The master and crew must understand at what angle the tug is approaching its limits and must communicate this to the pilot and ship’s bridge.

Crew positioning. During an assist with the towline under load, no crew member should be standing adjacent to the tow hook in the snap-back zone. Crew must be positioned to observe the towline angle and access the slip release — both requirements simultaneously.

Drill the release. The slip hook release must be practised, not just described. In a girting emergency, the time available to act is measured in seconds. The action must be instinctive.

Test Your Knowledge

Try a safety knowledge check at Crew Connect — tug girting and towline safety questions from this investigation.

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Sources: MAIB Safety Bulletin SB1/2026 (February 2026) | MAIB Report 17/2024 — Girting and capsize of tug Biter with the loss of two lives while assisting passenger vessel Hebridean Princess off Greenock, Scotland, 24 February 2023 | MGN 471(M+F) — Conventional Tugs: Preventing Capsize Through Girting | MSN 1833(M+F) Amendment 1 | GOV.UK/MAIB