Caustic Network and Barracuda

July 17, 2009


Photographer: Mila Zinkova
Summary Authors: Mila Zinkova; Jim Foster

I was peacefully taking underwater images of caustic optics when a mean looking barracuda (they always look mean) slowly moved into my viewfinder. A barracuda in shallow water and a shiny camera in my hands was perhaps not the best combination -- at least for me. I took one more shot (photo above) capturing not only the caustic but the barracuda and a sea urchin (lower left) and then quickly swam away, leaving the refractions and distortions of sunlight all to the creatures of the sea. Caustic networks form whenever the water's surface acts like a lens, alternately focusing and defocusing light. Those regions that are in rough focus are quite bright while those that are out of focus appear dark. Caustics are most noticeable when the water's depth is approximately five times the crest-crest wave distance. Swimming pools and shallow bodies of water often fit this description. Photo taken in May 2009 on the Big Island of Hawaii, off Kona Beach.