David Morris took a photo of the ship while walking near Falmouth, Cornwall.
BBC meteorologist David Braine said the "superior mirage" occurs because of "special atmospheric conditions that bend light".
He said the illusion is common in the Arctic, but can appear "very rarely" in the UK during winter.
Mr Morris said he was "stunned" after capturing the picture while looking out to sea from the hamlet of Gillan
Mr Braine said: "Superior mirages occur because of the weather condition known as a temperature inversion, where cold air lies close to the sea with warmer air above it.
"Since cold air is denser than warm air, it bends light towards the eyes of someone standing on the ground or on the coast, changing how a distant object appears.
David Morris took the photographs from the hamlet of Gillan, near Falmouth. Souce: BBC
Superior mirages can produce a few different types of images - here a distant ship appears to float high above its actual position, but sometimes an object below the horizon can become visible."