A new photo series explores the magic and beauty of an underwater universe, with incredible and detailed imagery of elusive marine life.
The winners for the Underwater Photographer of the Year 2015 cast light on an eerie and little-known undersea world.
Photographer Nuno Sá was awarded the title of overall winner for his intricate picture of a seahorse.
Other notable images in the competition included an ethereal photo of a diver called Angelita, by Fabrice Guerin, which was taken on Mexico's Yucatan peninsula and the sweet Good Luck My Babies, a photo of a seahorse and its children.
The winning image, entitled 50 Tons of Me, was picked by the judges because of its clever composition, as it looks like it has been lit from within. Photographer Nuno said in order to light the shot he had the "unusual accessories of two scientists, who were holding my strobes, 1 strobe behind and 1 over the seahorse".
Nuno took the photograph at the Natural reserve of Ria Formosa, which is home to the world’s largest population of the two species of seahorses found in the Mediterranean and Atlantic seas.
He then spent 10 days diving in this natural reserve for National Geographic Portugal, following a pioneering project between the University of Algarve with Project Seahorse that has been breeding seahorses in captivity.
The goal of the project is to repopulate areas where seahorse eco-systems have been reduced or extinct by fishing. Over 50 tons of seahorses are captured every year for ornamental purposes, and for use in traditional oriental medicine.
Judges in the Underwater Photographer of the Year competition presided over a selection of 2500 entries from 40 countries.
Take a look at more of our favourite winning and runner-up shots below
Above: British Waters Compact winner Trevor Rees with ‘Cuttlefish in a blur’
Trevor Rees/UPY 2015
Above: Up and Coming Worldwide winner Fabrice Guerin (France) with ‘Angelita’ taken on a Mexico’s Yucatan Peninsula in a cave called Cenote Angelita, at a depth of 30 metres
Fabrice Guerin/UPY 2015
Above: International Behaviour runner-up Tammy Gibbs with ‘Good luck my babies’
Tammy Gibbs/UPY 2015
Above: International Wrecks winner Tobias Friedrich with ‘Eelastic’, a picture of a giant moray eel taken inside the wreck of the Chrisoula K in the northern Red Sea
Tobias Friedrich/UPY 2015
Above: British Waters Macro winner: Trevor Rees (UK) with ‘The amphipod has landed’
Trevor Rees/UPY 2015
Above: International Macro, third: Filippo Borghi with ‘The Passenger’, a photo of an emperor shrimp on a solar powered nudibranch
Filippo Borghi/UPY 2015
Above: International Macro runner-up: Theresa A Guise (US) with ‘Dancing shrimp in formation’ taken on a dive site mooring, a large concrete block, which was covered in pink sponge
Theresa A. Guise/UPY 2015
Above: International Wide Angle category runner-up Morten Bjørn Larsen with ‘Bottoms Up’, an image of freediving world championships in Denmark
Morten Bjørn Larsen/UPY 2015
Above: International Wide Angle runner-up Hani Bader with ‘Socotra Cormorant’, a photo of jellyfish and Socotra cormorant in Bahrain
Hani Bader/UPY 2015
Above: British Underwater Photographer of the Year and British Waters Wide Angle winner Matt Doggett with ‘Gannets Feast’, shot off the Shetland Islands, UK
Matt Doggett/UPY 2015
Above: Underwater Photographer of the Year 2015 winner and International Macro winner Nuno Sá (Portugal) with ‘50 Tons Of Me’, taken in the Algarve Nuno
Nuno Sá/UPY 2015