Length of Britain
Time: 135 days
Hazards: Giant tankers, jellyfish, 7m waves
Respect rating: 7
This mammoth journey saw Sean Conway swim between one and 34km a day, with 45 days off due to bad weather. He got through six wetsuits, was stung by 10 jellyfish and threw up seven times. "I burst out crying when I finished," said Conway. "At times, the waves were huge and I was sick from drinking salt water. It's annoying to see 1,000kcal go to feed the fish."
Cuba to Florida (without a shark cage)
Time: 52hrs 54mins and 18 seconds
Hazards: Sharks, sunburn, storms, jellyfish
Respect rating: 10
It took five attempts, but Diana Nyad finally completed this swim in 2013, 35 years after she first tried it. She wore a full lycra suit, had a silicone mask to fend off jellyfish and a faint electric field around her to keep away the sharks. "When my mind goes and my right brain emerges I lose control of my intellectual thinking," she said. "I'm in a dream state."
Time: 7hrs 14mins (2013 winner)
Other Hazards: Strong tides, boat traffic, floating debris
Respect rating: 5
Flotsam and jetsam are the biggest challenges in this annual event, which first began in 1927. It runs a counter-clockwise circle around Manhattan from Battery Park City. Paul Newsom won in 2013 in terrible conditions. "It was the coldest MIMS on record by some margin at just 16°," he said. "Three swimmers were taken to hospital with hypothermia."
Ka'iwi Channel Swim
Other Hazards: Strong winds, giant waves, Man O'War jellyfish
Respect rating: 6
Slap bang in the middle of the Pacific Ocean, this swim runs between the Hawaiian islands of Molokai and Oahu – but it's far from paradise, with unrelenting winds, huge waves and strong currents. Just 28 people have completed it and organisers warn: "Because of the precedent set in previous swims, shark protection devices are allowed."
Time: 18mins 50 seconds
Temperature: -1.8 degrees
Hazards: Hypothermia, frostbite, polar bears
Respect rating: 9
In only a pair of Speedos, eco-campaigner Lewis Pugh took on the first long-distance swim across the Geographic North Pole – in a bid to highlight the effects of climate change. "It's a tragedy that it is possible to swim at the North Pole," he said after swimming in an ice crack. "The water was absolutely black and the pain was instant. It felt like my body was on fire."
The Amazon (all of it)
Time: 66 days
Other hazards: Piranhas, alligators, sharks, snakes, whirlpools, tidal waves and armed bandits
Respect rating: 11
The Danube, Mississippi and Yangtze rivers were not enough for Martin Strel. So for a scarier challenge he swam the Amazon. Completing 52 miles per day, sometimes against tides that pushed him backwards, he battled dizziness, nausea and diarrhoea to finish. "The animals just accepted me," he said. "I've swum with them so long they must think I'm one of them."
Time: 58 days
Other Hazards: Barges, jet skis, submerged logs, shopping trolleys, toxins
Respect rating: 9
Having never swum more than 100m in one go before, Dave Cornthwaite swam 7–14 hours per day from Chamberlain to St Louis. Sometimes he could see only three inches ahead, so a team of paddle boarders led the way. "My body reached its limit in the final three weeks," he said. "I vomited countless times each hour, almost once a minute through the last week."
River swimming, England
Temperature: Average 10–15°C
Hazards: Currents, swans, ducks, Weil's disease, fishing lines
Respect rating: 2
Ok, we're not going to pretend that taking dip in your local river is going to earn you massive bragging points. But jumping in a river and letting yourself be carried downstream is a great and invigorating adventure open to anyone who can swim. This image shows a swimmer in the river Stour, England. For more ideas, check out these wild swims and get exploring yourself: Wild Swimming: 300 hidden dips to the rivers, lakes and waterfalls of Britain.