Deep underground of the Yucatan Peninsula are ribbons of sub-terrain water systems, all interconnected. The Maya believed the entrances to these were the gateways to the underworld.
Where there is light penetration and organic debris, there can exist a spectacle of a Hydrogen Sulphide cloud suspended in the water.
This shot was taken at 30m down in The Pit cenote, near Tulum, Mexico.
The light you see is ambient light filtering down through the cave aperture some 40m up.
Thanks for taking time to look at my photography!