This photo shows a green sea turtle (Chelonia mydas) sharing its resting spot with a whitetip reef shark (Triaenodon obesus). As mismatched as this arrangement may seem, I've actually seen it several times and I imagine it must be fairly common. Both species like to shelter under ledges or in lava tubes during the day and, since such places are in short supply, inter-species co-habitation sometimes occurs. This type of shark has small teeth and feeds on small reef fishes and invertebrates so the turtle is not in peril. These species like to shelter in tight spaces so getting a pleasing photo of both creatures is difficult. Hence, the shark's face being obscured.
Also known by the Hawaiian name palani. This photo was taken at about 70' depth and early in the morning. This and a couple other palani were following me in hopes I would stir up some organic detritus for them to feed on.