Earlier this week, Brent Rossen posted a photo on Reddit that his girlfriend took of a rainbow swamp, and within 24 hours the photo received more than 120,000 upvotes. The couple was enjoying a walk at First Landing State Park in Virginia when they came upon the unusual phenomenon.

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“Me and my girlfriend were walking in the woods the other week and saw a rainbow pool for the first time,” Rossen wrote in his post.

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So how does this happen? Jeff Ripple, a former Florida swamp walk leader, told the BBC that the rainbow effect occurs because of the natural oils released by decaying vegetation. The decomposing leaves in the water release tannic acid and a thin film forms on top of pooled water in swamps and marshes. When the sunlight hits it at a certain angle, you can see the gorgeous colors.

However, if you look at the water in a shadow, it appears to be normal swamp water. But, on a sunny day, you can see the rainbow when you look at it from an angle. The water also needs to be still for a long period of time for the rainbows to appear. Ripple says that any movement from sheet flow, wind disturbances, or current will “destroy the fragile rainbow film.”

This phenomenon reportedly happens at various swamps and marshes along the Eastern seaboard. Retired engineer Michael Hussey posted a pic on Facebook of a rainbow pool in Tallahassee, Florida. Swamp walk leader Sandra Friend has also blogged about her experience with rainbow swamps, and Annie from Not Just Abroad has also posted about a rainbow swamp in Caw Caw County Park in Charleston, South Carolina.

Hussey says that he sees this happen every three to four years, and it is “beautiful to see.”

Thomas Thornton, facility manager at Caw Caw swamp, says that it must be the result of some kind of perfect storm, and it seems like you have to be lucky to see it in person.


Images via Shutterstock