Swimmers battle whitewater and waves.
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The world’s 7 most dangerous open-water swims

Only six people have ever completed all seven of these swims. These dips are definitely not for the faint-hearted!
By Emma Sheppard
4 min readPublished on
The Ocean’s Seven challenge was devised in 2008 by Steven Munatones, the founder of the World Open Water Swimming Association. It was proposed as the marathon-swimming alternative to the Seven Summits challenge, in which mountaineers have to climb the highest peak in seven continents. To date, at least 350 people have conquered the peaks but only six swimmers have completed the Ocean’s Seven. The swims can be tackled in any order, but English Channel rules apply to all – swimmers must only wear a normal swimsuit, hat, goggles and earplugs.

1. North Channel

The body of water between Northern Ireland and Scotland features heavy seas, cold water, jellyfish and strong currents. Kim Chambers (one of only three women to complete the Ocean’s Seven) didn’t take warm showers for six months to prepare for the low temperatures. She was stung more than 200 times during her swim in 2014 and had to be hospitalised after she’d finished because of all the toxins in her body. The swim stretches for 21 miles and is widely considered to be the most difficult in the world.

2. Cook Strait

The channel between the North and South Islands of New Zealand is a relatively short 16 nautical miles across – but the water is chilly and jellyfish and shark sightings are common. British swimmer Adam Walker described being accompanied by a pod of dolphins, which he believed were protecting him from a shark below. The weather is changeable and hypothermia is a real risk.

3. Moloka’i Channel

Also known as the Kaiwi Channel, you will find yourself swimming between the west coast of Molokai Island and the east coast of Oahu here. Expect strong currents, deep water (701m at its deepest point), and what the World Professional Marathon Swimming Federation calls “aggressive marine life”. Walker describes being stung by a Portuguese man o’war in Molokai, which caused him to lose feeling in his spine.
Listen to the harrowing open-water swim 64-year-old Diana Nyad made from Cuba to Florida:

4. English Channel

At the time of writing, an estimated 1,619 swimmers have swum ‘solo’ (i.e. not as part of a relay team) across the 21 miles between England and France. The youngest swimmer to complete it was 11 years old, while the oldest was 73. It can take up to two years to get a spot with the seven Channel Swimming Association pilots who are qualified to take swimmers across. Kim Chambers attempted an impromptu solo attempt after her relay race and had to abandon it after seven and a half hours. “I was so ill-prepared,” she said. “It was a humbling experience.”

5. Catalina Channel

Stretching between Santa Catalina Island and Los Angeles in California, the Catalina Channel is 21 miles long. It's comparable to the English Channel in terms of distance and water conditions, although it’s a little warmer. American Steve Robles completed the swim in 2013 and described it as “rough”. He said: “I’m not even sure how I got to the beach, I was in complete exhaustion.” Doctors later hospitalised him with hypothermia and said he’d had a mild heart attack.

6. Tsugaru Channel

The water between the Japanese islands of Honshu and Hokkaido is known for being unpredictable. Kim Chambers’ captain during her swim across the channel called it 'The Dragon’ because of the high winds and choppy waves. Luckily her swim in 2014 was relatively calm – “the dragon was sleeping," she said afterwards. Adam Walker was stung repeatedly in the face by jellyfish during his swim, and flipped over by the large waves. It was “the hardest thing I’ve done in my life,” he said. The channel is 12 miles at its narrowest point, but most swimmers take the 18-mile route between Kodomori Cape on Honshu and Cape Shirakami on Hokkaido.

7. Strait of Gibraltar

Swimmers on the strait between Spain and Morocco have heavy boat traffic, sharks and unpredictable water to contend with. Most attempts are made from Tarifa Island and span 10-12 miles. The majority of swimmers will finish the crossing in around four hours, but it can take up to eight hours if there are strong currents. David Walliams completed the swim for Sports Relief with Olympic rower James Cracknell in 2008 in just under four and a half hours. Despite its relatively short distance, the swim from Europe to Africa can be cold and crosses two busy shipping lanes. The English Channel motto, 'Prepare for the worst – hope for the best' applies here.