This is the larva of one of the large Predaceous Diving Beetles (Dytiscus sp.). If anything, these are even nastier and more voracious than they look! The image was taken last summer in my 2-gallon aquarium setup. 5D II, 100 mm macro, 1/80, f/16, ISO 100, MT24-EX macro twin flash (diffused), tripod. I cleaned up a lot of tiny bits of debris in the water that were illuminated by the flash. I used the darken/lighten center filter in NIK Color Efex Pro 4 to apply a subtle vignette. All comments are welcome and appreciated.