Iceni Legend / X18: When One Vessel Has No One Aboard

What Happened

On 19 September 2025, the 22.4-metre crew transfer vessel Iceni Legend was heading to a wind turbine in the Greater Gabbard Offshore Wind Farm to transfer personnel. At the same time, the 4.58-metre uncrewed surface vessel (USV) X18 was conducting an underwater survey in the same field. The two collided at 1213 in clear conditions — clear skies, a low sun, 0.5m swell, 10kt wind.

Iceni Legend sustained damage and water ingress to its port bow but returned to port under her own power, unassisted. X18 was catastrophically damaged and sank; its wreckage has not been recovered from the seabed. Nobody was injured — there was, of course, nobody aboard X18 to injure.

A Genuinely New Category of Question

This is a thin interim report by design — MAIB's investigation is complete and a full report is being prepared, but what's published so far is limited to the bare facts. What it does confirm is the shape of the investigation to come: MAIB is examining the environmental conditions, the ability of both vessels to see and communicate with one another, and the regulatory landscape surrounding maritime autonomous and uncrewed vessels.

That framing matters. COLREGS was written for vessels with someone aboard to keep a lookout, sound a signal, and take avoiding action. A USV conducting an underwater survey has none of those in the traditional sense — it may have sensors, it may be remotely monitored, but the assumptions baked into "stand-on vessel" and "give-way vessel" don't map cleanly onto a small, low-profile, uncrewed platform working in the same water as crewed traffic. The IMO's own work on a goal-based instrument for Maritime Autonomous Surface Ships (MASS) is directly relevant here — this collision is a live example of exactly the gap that work is trying to close.

Recommended Actions (Pending the Full Report)

1. If your vessel operates in or near an offshore wind farm or survey area, actively check for known USV operations before transit — don't assume a "clear" visual scan means clear of small, low-profile autonomous surface traffic.
2. A 4.58m USV is a genuinely difficult visual contact, even in good visibility with a low sun — treat radar and any available AIS/tracking data as essential, not supplementary, in areas with known uncrewed vessel activity.
3. USV operators: confirm your vessel's visual and radar detectability (reflectors, lighting, marking) meets or exceeds what's reasonable for the traffic density of the area you're operating in.
4. Follow MAIB's full report when published — this interim report doesn't yet establish cause, and jumping to conclusions about which vessel was "at fault" isn't supported by what's been published so far.

Test Your Knowledge

Think you've got this covered? Put it to the test in Crew Connect's free Knowledge Checker — try a quick COLREGS round and see how you score.

Related Reading

• Solong / Stena Immaculate: The Lone Watch in the Fog