David Fleetham / Blacktip reef shark (Carcharhinus melanopterus) swimming just below surface at sunset, split level view. Off the island of Yap, Micronesia.

David Fleetham / Whitetip reef shark (Triaenodon obesus) resting on sea floor. Kauai, Hawaii.

Jeff Rotman / Head and gills of juvenile Scalloped hammerhead shark (Sphyrna Lewini), Kane'ohe Bay, Hawaii, Pacific Ocean.

Claudio Contreras / Black grouper (Mycteroperca bonaci) and Caribbean Reef Shark (Carcharhinus perezi), Jardines de la Reina / Gardens of the Queen National Park, Caribbean Sea, Ciego de Avila, Cuba, January

Claudio Contreras / Silky shark (Carcharhinus falciformis) two swimming together, Jardines de la Reina / Gardens of the Queen National Park, Caribbean Sea, Ciego de Avila, Cuba, January. Vulnerable species.

Doug Perrine / Female scalloped hammerhead shark, Sphyrna lewini, off Keauhou, South Kona, Big Island, Hawaii, USA ( Central Pacific Ocean )

Doug Perrine / Female scalloped hammerhead shark, (Sphyrna lewini) off Keauhou, South Kona, Big Island, Hawaii, Central Pacific Ocean

Alex Mustard / Great hammerhead shark (Sphyrna mokarran) female at night with Bar jacks (Caranx ruber), South Bimini, Bahamas. The Bahamas National Shark Sanctuary. Gulf Stream, West Atlantic Ocean.

Alex Mustard / Great hammerhead shark (Sphyrna mokarran) male in shallow water. South Bimini, Bahamas. The Bahamas National Shark Sanctuary. Gulf Stream, West Atlantic Ocean.

Alex Mustard / Great hammerhead shark (Sphyrna mokarran) swimming over a sandy seabed, accompanied by Rainbow runners (Elagatis bipinnulata) South Bimini, Bahamas. The Bahamas National Shark Sanctuary. Gulf Stream,...

Alex Mustard / Whitetip shark (Carcharhinus longimanus) head on beneath the surface. Rocky Island, Egypt. Red Sea

Alex Mustard / Diver (Predrag Vuckovic) is dwarfed by Great hammerhead shark (Sphyrna mokarran). This species can reach over 6m in length. South Bimini, Bahamas. The Bahamas National Shark Sanctuary. Gulf Stream, We...