Stunned visitors to the Cornish coast were able to witness a boat as it appeared to sail across the sky as a result of a rare opitcal illusion usually seen only in the Arctic circle.

       The “flying” boat, caught in a rare “mirage”, was captured by photographer Martin Stroud after he spotted the phenomenon in Coverack.

       Posting on the Coverack Life facebook group, Mr Stroud said: “Almost looks like it’s flying! Beautiful day for a visit to Coverack.”

       In the image, the water on which the boat was sailing is so still it appears to have become the same colour of the sky.

       The picture has stirred-up much praise on the local group, with one user describing it as “an amazing shot”.

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       (Martin Stroud / SWNS)

       Similar phenomena has been witnessed before in Cornwall, but accompanied by differing explanations.

       In 2017, Rosie Patterson captured what appeared to be a “flying” container off the coast of the town of Porthleven.

       It was explained at the time as a rare state of conditions, in which the sea in the foreground of the picture was choppy, with waves, while further back out to sea, where the ship was anchored, the water was calm and mirror-flat - creating the illusion of the ship apparently sitting in the sky.

       But when a similar image was captured by David Morris at Gillan Cove back in March last year, a different commentary was offered.

       BBC meteorologist David Braine described as a “superior mirage”, which were common in the Arctic but happened only “very rarely” in the UK.

       (Martin Stroud / SWNS)

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       A superior mirage makes an image appear to be located above the real object, caused when the air below the line of sight is colder, and therefore denser, than the air above it.

       This is the opposite of what normally happens during the daytime and results in the light rays bending downwards as they pass through the so-called ‘temperature inversion’.