Magic of a rainbow swamp

Freak of light turns Caw Caw Swamp into a rainbow of colors. The phenomenon seems to happen occasionally during the winter.

RAVENEL — The moment is a wonder, even to people accustomed to a florid Lowcountry landscape of white squirrels, painted buntings, passion vines and rainbow snakes.

You can be walking the fringe of a cypress swamp in winter when a freak of sunlight, tannins, soil or something turns the blackwater into flumes of blues, greens, pinks, yellow and orange — a virtual cypress swamp rainbow amid the moss and earthen brown tree trunks.

“To stumble on something like that is so cool,” said Annie Martin of Hanahan, who was out on the swamp boardwalk at Caw Caw Interpretive Center on Sunday with her husband, Jeremy Martin. They were shooting wildlife photographs with his new zoom lens.

“We just saw all these amazing colors and started snapping,” said Martin, who blogged about it on

At the park, the phenomenon seems to happen occasionally during the winter, in a finger of Caw Caw Swamp along the trail, said Thomas Thornton, facility manager. Nobody really knows why.

Suspicions include a sheen of oils from the cypress trees, which also excrete the tannins that give blackwater its ebony tone. Some researchers have suggested an organic film from bacteria in the soil, or a combination of the two.

But nothing really explains the freakish quality to it: Time of day, extent of sunlight and the angle of the sun don’t seem to matter. The only real constant is still water. Photographers regularly turn out carting heavy-duty gear when they think the day is right but nothing happens.

“It’s some kind of perfect storm of conditions,” Thornton said. “It just seems like you have to get lucky.”

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