These stunning images show one man`s incredible 400 hour journey of endurance swimming in the coldest waters in the world. In a breathtaking feat of dedication to his profession, extreme diver Norbert Wu captured the visual feast swimming under Antarctica`s captivating sea ice. Over the past 12 years he has braved the bone-chilling temperatures of the planet`s most southern continent to piece together his mesmerising collection. Majestic emperor penguins fizz through the water like rockets while alien-looking star fish and anemones carpet the busy ocean floor. But when cute animals and bizarre creatures are not playing Wu`s camera, vast icy caverns and mammoth underwater chambers have allowed him to paint a spectacular view of secret worlds of ice around Antarctica. Since the 48-year-old American from Atlanta, Georgia, first visited the vast frozen landscape in 1997, Norbert`s love of the dangerous region has grown year on year. Over seven trips to Antarctica photographer and cameraman Norbert has travelled nearly 200,000 miles to the American Antarctic research stations at McMurdo and Palmer to get his pictures. Diving six days a week for 12 weeks each visit, he has amassed over 1,000 Antarctic dives equalling an astounding 17 days submerged in the frosty depths. He said: "The water around McMurdo Station is some of the coldest water in the world at -1.8c but it is worth it when you see what is down there. "At dives like that you work very hard to keep the danger out of what you are doing. How cold you get is a very psychological thing. "One of the coldest I have ever been in my life was when I decided to assist another diver. Without my camera and without something to focus on meant the cold started to win." Despite his calmness about the danger of his work, brave Norbert and others like him are facing a hostile environment where just 90 mins in the water could chill you to death. His epic adventures to the vast world of snow and sub-zero temperatures and seen him contributing to over 20 books and a number of TV projects. Going boldly where few men and women dare, Norbert`s passion for underwater photography has seen him working on pioneering documentaries including the BBC`s Life series currently being screened in the UK for the first time. "The first stage is logistical," he said. "Readying the dive and camera gear, and then loading it and then driving to the dive site. "There are lots of details to consider and track, and a moment of absent-mindedness will result in a miscalculation or forgetting something crucial, ruining a dive. "Then it`s about getting into the dive gear, making sure everything is connected, seated right on my body and functioning properly. "Finally you slip into the water, usually through an hole in the ice drilled for you several feet deep. You reach up to take camera gear being handed to you before dropping down a bit underwater and checking the camera to make sure it isn`t leaking and that it is functioning properly. Then you head off to what it is we want to shoot." Despite the specialised nature of his work, Norbert didn`t always plan to be floating around under groaning sheets of ice in a lonely world. "Many scuba divers get interested in underwater photography after they start diving in order to record what they see for their enjoyment. It was just a natural progression from there." "I didn`t start underwater photography thinking it would lead to anything. But you never know where life will take you, and if you had told me long ago that I would be doing what I`m doing now, I wouldn`t have believed you." Even after the shocking amount of time he has swam at sub-zero temperatures, Wu said his health has remained relatively in tact. "After my first season in 1997 I spent a couple of years with stiff hands. They weren`t as flexible as they used to be. I was pretty alarmed at that but it has either gone away or I don`t notice it any more. That`s the only negative physical thing I`ve experienced." On his unstoppable skirmish into the cold blue oceans that surround Antarctica, Norbert will return to Antarctica`s Palmer station when he will finish his next project documenting the area`s marine life.