A mind–boggling mirage off the coast of Cornwall has left spectators baffled. 

On 24 May, several visitors reported seeing objects floating on the water. 

The objects would appear and disappear and change in sharpness and shape, and ranged from 'huge bears' to 'AT–AT Walkers'. 

Commenting on St Ives Boats' post about the mirage on Facebook, one spectator suggested: 'Ghost ships in the mist from years gone past.'

Another said: 'Looked like pi sinking into the sea.' 

And one joked: 'I saw this too and thought I was losing my marbles!' 

Now, experts have revealed the simple explanation for the 'objects' – a special type of mirage known as Fata Morgana. 

'We were looking at a mirage. A Fata Morgana is a complex form of mirage visible in a narrow band right above the horizon,' said St Ives Boats. 

A Fata Morgana mirage causes objects to appear to hover in the air just above the horizon – whether it's ships, coastlines, icebergs, or even entire cities.

The name is an Italian term, named after the Arthurian sorceress Morgan le Fay, who believed that these mirages – often seen in the Strait of Messina – were fairy castles in the air.

For the mirage to appear, there must be a layer of cold, dense air sitting near the ground or sea, with warmer air above it. 

As light passes through these layers, it refracts (bends) strongly, producing inverted and erect images.

In this case, ships miles away from the Cornwall coast were made to appear as if they were much closer to land – and much bigger.

'A Fata Morgana superior mirage of a ship can take many different forms,' explained SKYbrary.

'Even when the boat in the mirage does not seem to be suspended in the air, it still looks ghostly, and unusual, and what is even more important, it is ever–changing in its appearance. 

'Sometimes a Fata Morgana causes a ship to appear to float inside the waves, at other times an inverted ship appears to sail above its real companion.'

St Ives Boats described the mirage as 'surreal'. 

'It was surreal seeing these huge "structures" and weird atmospheric changes and we and our passengers were just stunned at times,' it said on Facebook. 

'We're sure that it was a visual distortion of the carrier and others of container ships all of which by this point were many miles away.'

This isn't the first time a Fata Morgana illusion has caught viewers off guard. 

Multiple 'floating ships' have been photographed and videoed over the years, with boats appearing to hover off the coast of Britain in Cornwall, Devon and Aberdeenshire in one incident.

In another sighting, four ships appeared to hover above the sea off the coast of Cyprus, forming a line just east of the southern city of Limassol.