Underwater nature photography is a tough job.
To get the perfect shot, photographers brave freezing waters, pitch-black diving expeditions, and hungry predators. Sometimes, they wait days for the right moment to snap a picture of a reticent seahorse or a swift shark.
The annual Underwater Photographer of the Year competition brings together the best photos of creatures lurking beneath bodies of water.
Here are the top three award-winning underwater photos in every category. You can see last year's winners here.
Captions have been condensed and edited for clarity.
Underwater Photographer of the Year winner: "CYCLE-WAR" by Tobias Friedrich
"For a few years now I had had this image in mind as the motorcycles on this truck inside the Thistlegorm lie so perfectly together, but you can only barely capture it because the wall is very close and you can't move backwards enough to capture the whole scenery. As a result I had to create a panoramic image of the same scene to capture the whole cargo deck, including some lights that give the image more depth."'
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British Underwater Photographer of the Year winner: "Love Birds" by Grant Thomas
"I chose Loch Lomond as the location for this shot due to its idyllic scenery, water access and friendly swans. My initial idea was to frame a split shot of one swan feeding below the surface of the water but when I noticed how comfortable they were around me I was confident, with some patience, I could get that magical shot of the two. It was mid-day, sun high in the sky, I waded slowly into the shallow water, allowing the swans to become comfortable with my presence. When they began searching for food below the water line I just had to wait for that perfect moment of synchronicity."
Most Promising British Underwater Photographer winner: "How many pike?" by Tony Stephenson
"I love photographing pike and on this particular dive during the Easter holidays, a 'group' of males were looking for a mate. Once they found one they pursued her relentlessly and were completely transfixed on gaining her attention. This allowed me to get close in front of the fish, fill the frame and aim to get lots of good eye contact. I was delighted by the results."
Up and Coming Underwater Photographer of the Year winner: "ROAR" by ManBD UiDive
"When I was shooting this nudibranch I was focusing on its behaviour to get just the right shot. While this happened a moray eel suddenly appeared out from the blue behind the nudi. To my surprise, another nudi appeared right behind the other one maybe to mate. I then decided to wait a while longer for the nudi to be in frame with the moray eel roaring behind. It took about 30 minutes to get this shot and it was well worth it."
"Evening Snorkel" by Brook Peterson
"I was practicing sunset split shots in the calm waters around Ras Um Sid when I noticed several people walking down the pier with snorkel gear. My first thought was to wait until they were out of the way, but then I realized that THEY were the story. I wanted to preserve how the colors in the sunset seemed to mimic the colors of the corals so I decided a silhouette shot would meet my needs best."
"Surrounded" by Fan Ping
"Shark behaviourist Ms. Cristina Zenato has been studying Caribbean Reef Sharks near Freeport in The Bahamas for over 24 years. The unique bond between her and the sharks allows her to get really close to them without putting them into tonic immobility and this has been helping many scientists, photographers and conservationists better understand and protect this beautiful species."
"Humpback Whale Spy Hopping" by Greg Lecoeur
"Tonga offers probably the best opportunity to interact with the whales in blue water. Although weighing several tens of tons this mammal showed incredible agility and power in holding itself vertically in the water. It was very impressive and we could feel the power of nature but we were also invaded at the same time by a feeling of gentleness. I had the chance to freeze this moment with a split shot to recreate a spectacular moment."
"The Shadow" by Kenji Cheow
"Creating shadow for underwater images is always challenging. When I found this goby on a halimeda algae on the sand, I knew it would be a perfect subject for my 'Project Shadow.' I began with slowly placing a white slate behind the subject, shining my torch to get the angle for the shadow and then another torch to light up the subject. Then, I patiently waited for the moment."
"Friend or Food?!" by Songda Cai
"I've had many encounters with this conger eel and I've taken a few photos, but never have I seen it in such a picturesque manner as this, as if drawing you in by coiling its body and at the same time darting its eyes on a lone prey."
"Seahorse Density" by Shane Gross
"The pond I was in has the highest density of seahorses on Earth, but I've never seen three together like this before. I was camping on shore and had all night to shoot with the idea of backlighting a single seahorse, but finding three together was a real gift."
"Curled Octopus" by James Lynott
"This photo was taken during a fantastic day diving at St. Abbs. The dive had started at the large gully at West Hurkers and we were making our way towards the Anemone Gullies when I spotted this octopus nestled amongst the soft corals which cover the boulders and bedrock here."
"Intertwined Mute Swans" by Ian Wade
"I've been photographing mute swans underwater for a few years now in different locations in Bristol & Somerset. On this particular day at the Floating harbour in central Bristol, two mute swans came over to investigate me on a pontoon."
"Scratchy Seal" by Vicky Paynter
"The Farne Islands are home to thousands of grey seals (also known as Atlantic seals), and each autumn hundreds of pups are born here. We'd arrived just before then but there were still plenty of younger seals keen to interact and explore these strange bubbling divers."
"Colorful Corkwing" by Kirsty Andrews
"Male corkwing wrasse can be stunning and I had wanted for some time to take an image that would show off the personality and vibrant coloration of this common UK critter."
"Topshell Tapestry" by Cathy Lewis
"During a dive on the Manacles I came across a Painted topshell on a furry-looking kelp blade. This fluffy growth is actually a hydroid, made up of zigzag strings of tiny organisms."
"Battle of the Tompots" by Henley Spiers
"Despite appearances, these two Tompot Blennies are not kissing but engaged in a ferocious battle over mating rights. The British summer is mating season amongst Tompots and competition is fierce."
"Fresh Otter at Sea" by Greg Lecoeur
"I was very intrigued by this mammal who adapted to marine life and had in mind to witness of this scene, so I asked to my Scottish friend Richard Shucksmith who knows this species very well to help me to capture this image. During a dive we were very lucky to find this otter who was curious about my lens."
"Migration" by Austin Ferguson
"Every year in the Pacific Northwest of North America, wild Pacific Salmon make an epic migration from the ocean up the same rivers and streams that they were born in, sometimes traveling over a thousand miles inland to reproduce. Over the course of three months, I spent countless hours in 13° C (55° F) water photographing this incredible migration. Eventually, my patience paid off when I captured this image of a male Pink Salmon fighting his way back upstream to continue his species and nurture the surrounding ecosystem."
"The Hammer" by Jacob Degee
"The Great Hammerheads were slowly circulating around us. It was my last chance. The last opportunity to do what I had in my mind for months. 'Stay calm, be patient' was constantly echoing in my mind. Sitting on a soft sandy bottom, facing against the sun I could have only waited. And there she was coming directly at me."
"Frogfish Illusion" by Ipah Uid
"Two items were used to create this shot: a cokin filter and a plain old CD. Being a compact user, I love experimenting on new techniques."
"Flower Power" by Jack Berthomier
"This picture shows three blennies that gather by the dozen under a sheltered spot. In this image, they are hiding under a floating hibiscus flower."
"Dancing With The Giants" by Simone Matucci
"These two adult humpbacks had such a connection with us in the water, literally 'dancing.' It was probably the most wild and incredible thing I have witnessed in my entire life."
"Angels of the Deep" by Santosh Shanmuga
"These sandbar sharks are all male and have probably come together to feed or spawn. A school of females may join them later in the season but in the meantime, they must establish a hierarchy. Sizing each other up, the dominant sharks attempt to secure the better spots nearer the surface."
"Graceful manta" by Sylvie Ayer
"Diving with a manta ray one is always full of emotions. One of the best places in the world to dive with them is the Maldives. You can even meet them on a night dive just off the back of the boat. The manta come to feed and do some looping just at the surface. It is just fantastic!"
"Crocodile Reflections" by Borut Furlan
"When diving was finished for the day, I asked the divemaster to take me back again to a place where seawater crocodiles are usually seen. When we arrived, the sun was already on the horizon and it was very dark in the water. Fortunately, the crocodile was very cooperative and since we were both very calm, beautiful reflections appeared on the surface."
"Under The Wave" by Rodney Bursiel
"I have been traveling with musician and professional surfer, Donavon Frankenreiter for about four years now. On a recent surf trip to Tavarua, Fiji, I captured this shot of Donavon playing under the wave at Cloudbreak."
"The Nose" by Mike Korostelev
"The picture was taken in Kuril Lake, the place with the highest concentration of bears on our planet. The bears here are not hungry (due to the annual mass spawning of sockeye salmon) so they get used to people and do not feel danger from them."
"A Sand Tiger Shark Surrounded By Tiny Bait Fish" by Tanya Houppermans
"As I slowly swam to the center of the bait ball, I looked up and noticed a sand tiger a few feet above me. I swam on my back underneath her, trying not to startle her. As I moved with the shark through the water the bait fish parted way, giving me a clear shot of the underside of this beautiful shark, and also one of the most incredible experiences I've had yet as an underwater photographer."
"Gannets feeding" by Greg Lecoeur
"With the decline of fish stocks, gannets have to fight against food competition for their survival. They have learned to catch dead fish spilled overboard from fishing vessels and from bird watching boats that take advantage of this to attract them."
"In Hiding" by Scott Gutsy Tuason
"Taken at a depth of 15 meters in 200-250m deep water. Towards the end of the 'Blackwater' dive, Edwin, one of our divemasters, called me over to show me this beautiful jellyfish, for me only to realise it had a juvenile trevally within it, and to my amazement, it was wedged between the bell and the tentacles!"
"The Fisherman" by Filippo Borghi
"In winter time in the Izu peninsula in Tokyo area, the Asiatic cormorant stops for a couple of months before moving to China. This is the best moment to try to shoot this amazing sea bird during diving and fishing."
"Truck Nobia" by Tobias Friedrich
"The Zenobia wreck still contains about 100 trucks that sunk over 30 years ago, when the ferry sunk very near to the city of Larnanca. To capture the truck I placed an additional strobe inside the cabin and into my buddies hand to create some atmosphere of this very special dive site."