HMS Gannet's duty observer, Lieutenant Angela Lewis said: "Conditions were extremely challenging.
"Sea spray from the waves was being whipped up to a height of about 60ft in places and we were in the hover at about 80ft, so it was quite nerve-wracking."
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Cloud and outbreaks of rain will ease away eastwards during the morning, clearing the east coast around midday with sunny spells developing.
Police and emergency services are attending the scene.
Rebel-held east remains at risk while the pumping station supplying the western part of the city is once again in operation.