A crewman was airifted to hospital after his leg was crushed on a merchant ship off the coast of Moelfre.
Emergency services were called out at around 10.45am on Friday morning following the accident during lifeboat derrick operations on board the 182m Bulk Carrier, which was anchored around six nautical miles north of Anglesey.
The RNLI's all-weather lifeboat from Moelfe and the coastguard helicopter from Caernarfon both attended the scene.
The crewman in his 30s had suffered a severe lower leg injury - a significant double break and deep lacerations - after getting caught in heavy machinery on the second deck.
He was treated at the scene by the ship's crew, who managed to stem the bleeding, before the RNLI volunteers and the helicopter paramedic took over.

The crewman was then winched to safety and taken to Liverpool, where he underwent specialist surgical treatment.
Vince Jones, coxswain at RNLI Moelfre, said: "This was a fantastic multi-agency operation to safely treat, stabilise and evacuate a man in urgent need of specialist medical attention."
"Our crew bravely scaled the ship's 10-meter pilot ladder with equipment and all to reach the casualty in less than 30 minutes after we received the call."
"Time was critical, and without the combined efforts of the ship's crew, our volunteer lifeboat crew and rescue helicopter team, the outcome could have been very different. We wish the crewman a speedy recovery and thank all those involved in a successful outcome."


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