Disney's Sebastian the crab was a strong believer that life below the waves trumps a terrestrial existence (the Caribbean crustacean even put on an extravagant musical number to prove his dedication to aquatic life). After browsing through the winning entries in this year's Underwater Photographer of the Year competition, we're starting to think Sebastian might be have been onto something. From migrating mobula rays to feasting sharks (and even a rare appearance from an otter), we've rounded up our favourite photos from the 2018 competition. So sit back, relax and prepare to be wowed.

Swarm. Shrimp anyone? Photographer Rick Ayrton spotted these mysid shrimps with their glowing pink brood pouches near Swanage Pier in South West England. "I had no idea what I had captured until I downloaded the images for review," Ayrton says. © Rick Ayrton/UPY2018
Roar. With their peculiar shapes, extravagant colours and intricate patterns, nudibranchs make for great photographic subjects, and the sea slugs are a fair bit more dramatic when photographed against a backdrop of "hungry moray eel"!  © ManBd UiDive/UPY2018
Love Birds. Photographer Grant Thomas squelched through the idyllic waters of Scotland's Loch Lombard to capture this perfect image of intertwined swans. His wading was well-rewarded: the shot earned him the title of British Underwater Photographer of the Year 2018. © Grant Thomas/UPY2018
Basking Shark Feeding. While this massive-mouthed giant looks like it could swallow you whole, there's no reason to fear the weird creature: basking sharks are filter feeders. The behemoths spend their time lumbering along near the surface, mouths ajar, trying to scoop up plankton and small fish. This particular one was photographed in the rich waters off the Inner Hebrides archipelago during an annual migration. © Will Clark/UPY2018
How many pike? Photographer Grant Thomas was able to snap this close-up shot of a group of male pike as the freshwater fish were transfixed by a nearby female. © Grant Thomas/UPY2018
Blue Nudibranch. To capture this stunning shot of a nudibranch, photographer Ace Wu made use of blue lighting to help make his subject pop out of the frame. If the technique is done right, as it is here, it produces "an image of arresting beauty," said UPY judge Peter Rowlands. © Ace Wu/UPY2018
Morning Flight. Each Spring off the coast of Baja California, the Sea of Cortez becomes a temporary home for thousands of migrating mobula rays. Last year, photographer Filippo Borghi made sure that he was in the best spot to capture the rays in all their graceful glory. © Filippo Borghi/UPY2018
Crocodile Reflections. Swimming with crocs is a not past-time that appeals to all, but for photographer Borut Furlan, the reward is worth the risk. "Fortunately the crocodile was very cooperative," explains Furlan who captured this mesmerising photo in Cuba. "I shot many images with his reflections and this one was my favourite." © Borut Furlan/UPY2018
Gannets Feeding. "I captured this image in Scotland during summer time," explains photographer Greg Lecoeur. "Gannets hunt pelagic fish like mackerel by diving into the sea from a height of 30 metres, achieving speeds of 100 kilometres per hour as they strike the water and pursue their prey underwater. With the decline of fish stocks, gannets have to fight against food competition for their survival. They have learned to catch dead fish spilt overboard from fishing vessels and from bird-watching boats that take advantage of this to attract them." © Greg Lecoeur/UPY2018
Tiger Sharks Feeding On A Sperm Whale Carcass. No gallery of underwater photos would be complete without a shot of a shark chomping on something! Tiger sharks are known to consume a variety of prey (from condoms to porcupine quills), so this rotting sperm-whale carcass off the coast of Bermuda was definitely on the menu. Photographer Chris Burville mounted his camera on a pole to capture a close-up shot of the action.  © Chris Burville/UPY2018
Seahorse Density. This trio of seahorses silhouetted in a soup of planktonic prey was photographed in a secret spot in the Bahamas that allegedly contains the highest concentration of seahorses on Earth. © Shane Gross/UPY2018
Friend of Food?! "It is because of breathtaking sights like this that I fell in love with underwater photography," writes Songda Cai who snapped this dazzling image of a coiled conger eel staring at its prey. For UPY judge Martin Edge, the shot is one of the standouts from this year's competition. © Songda Cai/UPY2018
Fresh Otter At Sea. The Underwater Photographer of the Year competition is not all sea slugs and sharks; mammals, like this playful otter, make the occasional cameo too. Otters have all but vanished from England and Wales, but can still be found in Scotland’s cleanest bodies of water in the north and west where the species is making a strong recovery. Sometimes erroneously called sea otters for their tendency to occasionally plunge into the Big Blue in search of food, this is actually a Eurasian otter (Lutra lutra), and should not be confused with its North American cousin. © Grey Lecoeur/UPY2018
Oceanic Whitetip Shark. Pilot fish have a mutualistic relationship with oceanic whitetip sharks: in exchange for protection from predators, pilot fish work as all-round hygienists for the sharks, plucking parasites off their skin and swimming into their mouths to pick out fragments of food from between their teeth. © Greg Lecoeur/UPY2018
Elvis. The hairy or striated frogfish is hardly the prettiest fish in the ocean, but what it lack in good looks it makes up for in charisma. These odd-looking creatures are known for their ability to "walk" on the ocean bottom using their pelvic fins. This useful talent helps them secure the perfect spot from which to ambush any unsuspecting prey - a skill at which they are very accomplished. © Stefano Cerbai/UPY2018
In A Sea Of Squirts. "Velvet swimming crabs, with their red eyes and blue pincers are a popular subject," wrote photographer Paul Kay who captured this image in the waters off the west coast of Scotland. "This one caught my eye not because it was in itself photogenic, but because it was hunkered down on a rocky reef dominated by vase sea squirts (Ciona intenstinalis). Whilst these sea squirts are common enough in sea lochs, in this particular spot they were really clean and about as abundant as I can ever remember seeing them. So, for an animal which mostly tries to be relatively inconspicuous, this one had failed pretty miserably." © Paul Kay/UPY2018
Moons Above. "The swarming mass of pulsating animals, set against the striking emerald green water of the sea loch was quite hypnotic," Lucy Kay wrote about the experience of photographing a swarm of moon jellyfish off the coast of Scotland. These jellies are found throughout most of the world's ocean and are easily recognisable by their four brightly coloured gonads (yes, you read that correctly). © Lucy Kay/UPY2018
Pretty Lady. Pink is the new black! Pygmy seahorses are among the most accomplished camouflage experts in the ocean. Measuring in at about two centimetres, these tiny creatures typically seek refuge in soft corals or sea grasses and can be very difficult to spot. © TianHong Wang/UPY2018
Blacktip Rendezvous. Shy and easily frightened, blacktip reefsharks are often found in large groups to ensure safety in numbers. Photographer Renee Capazzola spent several afternoons in the water trying to capture this challenging over-under shot and hopes that the image will "capture peoples' attention and help raise awareness for sharks and other marine animals throughout the world." © Renee Capozzola/UPY2018
In Hiding. Juvenile travelly fish are known for their habit of using jellyfish like full-body gooey shields to help defend against predators, but this particular fish put on the perfect pose. "I had seen many Jack and Jelly combos before but never like this," explains photographer Scott Gutsy Tuason. "I shot around 20 frames and right on the last few frames it turned towards me to give me this very unusual portrait of a behaviour I had never seen before." © Scott Gutsy Tuason/UPY2018
Hummingfish. Is it a bird? Is it a plane? Nope, it's a fish with wings. There are over 40 known species of flying fish all with specially adapted pectoral fins that allow them to glide through the air for short distances in order to avoid predators. © Grant Thomas/UPY2018
Cycle-War. And the winner is ... Tobias Friedrich! Friedrich was given the title of Underwater Photographer of the Year 2018 for his wide-angle shot of a wreck featuring Norton 16H motorbikes with a school of soldierfish circling above. UPY Judge Peter Rowlands had this to say about the photo: "This is a quite extraordinary shot which must be viewed as large as possible. The bigger the better. And yet it is of a subject which has been photographed literally thousands of times. The artistic skill is to visualise such an image and the photographic talent is to achieve it. Perfectly lit and composed, I predict that there will never be a better shot of this subject from now on." © Tobias Friedrich/UPY2018