A healthy reef area, like this one off the coast of Castello Aragonese near Naples, Italy, is full of life, made up of a variety of coral species, and inhabited by a wide array of fish and invertebrates like the red sponges that dot the coral here. A well-camouflaged fish (a tompot blenny) hugs the coral just above the black sea urchin (bottom left).
David Littschwager /National Geographic Creative