At night this lemon shark (Negaprion brevirostris) lurks at the surface, but often during the day they will lie on the ocean bottom. This behavior had been thought to save them energy, but in reality it takes energy for the shark to push water over their gills while not moving. They may be lying still to be cleaned by small fish, like the wrasse.
“As nightfall was approaching and the sun setting before my eyes, I wanted to steal a quiet moment with one of the lemon sharks we had been photographing that afternoon. This particular shark was just as curious as I was, which enabled me to capture such an amazing shot. His eye came just above the surface and stared back at me as if to show me he was watching, while below the surface his mouth opened to reveal his sharp teeth.” -- Nature's Best Photographer, Deano Cook