As the sun descends a second sun rises from the water. Eventually
the two join at a red hued vertically stretched 'stem' (4th image
- larger version here).
Jules Verne likened this appearance to an Etruscan vase. The
stem shortens and thickens until the two suns (6th image) appear
like a Greek letter omega. The
suns continue to merge until eventually only a discus shape remains.
Sometimes the discus shrinks to finally form an I-Mir green
flash as in this example showing a similar
The lower sun is not a reflection from the water. It is
an 'inferior mirage', so named not from any poverty in appearance
but because the miraged sun is below the 'real' one. The
lower sun is an inverted image produced by refraction by a layer
of warmer and less dense air close to the ocean surface. The discus
shape is a combination of the upper limb of the erect sun and an
inverted image of it beneath. A fuller explanation and a ray diagram
are here in
the section about green flashes.