Kirkendall-Spring / Hills in the Lamar Valley, in snow, Yellowstone National Park, Wyoming, USA, February 2013.

Jouan Rius / Antelope Canyon, a slot canyon with eroded sandstone patterns, Navajo Tribal Park, Arizona, USA, December 2012.

Jouan Rius / Gypsum sand dune at sunset, White Sands National Park, Chihuahuan Desert, New Mexico, USA, December 2012.

Jouan Rius / Sandstone monoliths, Colorado Plateau, Kodachrome Basin State Park, Utah, USA November 2012

Franco Banfi / Great Blue shark (Prionace glauca) viewed from above, Pico Island, Azores, Portugal, Atlantic Ocean

Franco Banfi / Shoal of Sleek unicornfish (Naso hexacanthus) Maldives, Indian Ocean

Juergen Freund / Indo-Pacific bottlenose dolphin (Tursiops aduncus) just below sea surface in flat calm water. Raja Ampat, West Papua, Indonesia, February 2010

Richard Robinson / Grey Unicornfish (Naso caesius) and Sleek Unicorn fish (Naso hexacanthus ) school at Banc Lorne, New Caledonia.

Constantinos Petrinos / Traditional windmills, and luxury yachts, including the luxury ship Wind Star, which is a sleek, 4-masted sailing yacht. Mykonos Island, Cyclades, Aegean Sea, Mediterranean, Greece, August 2007

Constantinos Petrinos / Traditional windmills, and luxury yachts, including the luxury ship Wind Star, which is a sleek, 4-masted sailing yacht. Mykonos Island, Cyclades, Aegean Sea, Mediterranean, Greece, August 2007

Constantinos Petrinos / Traditional windmill, and luxury ship Wind Star, which is a sleek, 4-masted sailing yacht. Mykonos Island, Cyclades, Aegean Sea, Mediterranean, Greece, August 2007

Constantinos Petrinos / Traditional windmill, and luxury ship Wind Star, which is a sleek, 4-masted sailing yacht. Mykonos Island, Cyclades, Aegean Sea, Mediterranean, Greece, August 2007

Pascal Kobeh / School of Yellowback fusiliers (Caesio xanthonota) and Bluekeel unicornfish (Naso hexacanthus) Madagascar. Indian Ocean.

Thomas Lazar / Elephant Canyon, Needles Section, Canyonlands National Park, Utah, Colorado Plateau, April 2010.

Philippe Clement / Jackdaw (Corvus monedula) perched on branch in relaxed posture with sleek feathers, Belgium, June.

Jeff Rotman / Sleek / Blacktongue unicornfish (Naso hexacanthus) on coral reeef at night, Red Sea, Egypt

Juan Carlos Munoz / Grey seal {Halichoerus grypus} in surf, Donna Nook, Licolnshire, UK

Jeff Rotman / Blacktongue / Sleek Unicornfish (Naso hexacanthus) portrait. Egypt, Red Sea.

Angelo Giampiccolo / Precious sculptures line the ultra modern and sleek corridor on the 35-metre Gaia motoryacht model, created by Cantieri Maiora, Italy.

David Fleetham / Sleek unicornfish (Naso hexacanthus) gathering at a cleaning station on a reef waiting for the attention of one Hawaiian cleaner wrasse (Labroides phthirophagus), Hawaii, Pacific Ocean.

Georgette Douwma / Surgeonfish, composite image on black background, Yellowtail tang (Zebrasoma xanthurum), Powder-blue surgeonfish (Acanthurus leucosternon), Elongate surgeonfish (Acanthurus mata), Striped surgeonfish...

Georgette Douwma / Blacktongue unicornfish (Naso hexacanthus) composite image showing variation in marking on black background, Maldives, Indian Ocean.

Georgette Douwma / Surgeonfish composite image on black background, Bluespine surgeonfish (Naso unicornis), Striped surgeonfish (Acanthurus lineatus), Sailffin tang (Zebrasoma veliferum) juvenile, Mimic surgeonfish (Aca...

David Fleetham / Sleek unicornfish (Naso hexacanthus) at a cleaning station with a Hawaiian cleaner wrasse (Labroides phthirophagus), Molokini Islet, Maui, Hawaii, Pacific Ocean.

David Fleetham / Three Sleek unicornfish (Naso hexacanthus) at a cleaning station with a endemic Saddle wrasse, (Thalassoma duperrey) Hawaii.

David Fleetham / Sleek unicornfish (Naso hexacanthus) which has turned a darker than normal colour to help an endemic Hawaiian cleaner wrasse, (Labroides phthirophagus) spot parasites, Hawaii.