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.

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.

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

Jordi Chias / Split level view of Blue shark (Prionace glauca) at surface at sunset, Azores Islands, Portugal, Atlantic Ocean

Franco Banfi / Tiger shark (Galeocerdo cuvier) Northern Bahamas, Caribbean Sea, Atlantic Ocean.

Franco Banfi / Scuba diver and Tiger shark (Galeocerdo cuvier) Northern Bahamas, Caribbean Sea, Atlantic Ocean. March 2009.

Franco Banfi / Lemon shark (Negaprion brevirostris) Northern Bahamas, Caribbean Sea, Atlantic Ocean

Claudio Contreras / Bull shark (Carcharhinus leucas) Playa del Carmen, Caribbean Sea, Mexico, January.

Richard Robinson / Blue shark (Prionace glauca) just below surface, Hauraki Gulf, Auckland, New Zealand, June.

Richard Robinson / Blue shark (Prionace glauca) viewed from below, off the coast of Hawke's Bay, New Zealand, February.