Mysterious disappearance of ‘world’s greatest’ free diver

Every sport comes with some element of risk, whether it's achilles tendon injuries for sprinters, or the long term neurological impact of boxing.

But the risks of one sport in particular capture public imagination more than many others, simply because of how scary it is to people who don't partake in it.

This sport is, of course, free diving.

Natalia Molchanova was a Russian champion free diver, becoming the first woman to dive past 100 meters on constant weight, as well as the first woman to dive through the infamous Arch at the Blue Hole in Egypt - one of the world's deadliest diving spots - in one breath.

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Many popular free diving, such as the Blue Hole in Egypt, are used for the sport because they are very sheltered and therefore the risk of currents is lower.

However, in 2015 Molchanova was diving off an island in Spain, in a place where currents were a much higher risk, in more open water.

She had been leading classes, accompanying students down on their dives - with her being the only experienced diver in the water.

According to her son, Molchanova would have dropped a 20-metre line, as is the standard for beginner divers, as their descent would gradually get lower.

On the Sunday she had also been diving solo in between the classes. At the time, Kimmo Lahtinen of the freediving governing body AIDA, told The Guardian: "Never do it alone."

Some people believe that it was the factor of underwater currents which led to her disappearance while diving solo, even though she only dived to a depth of around 35 meters, much less than what she would be used to.

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She went down and tragically never resurfaced.

A search operation was started to try and find her, including helicopters and a robot combing the waters around where she disappeared in an attempt to find her.

But when it found no trace, rescuers - including her own son - came to the conclusion that she was gone.

The Spanish authorities called off the search for the veteran athlete on the Wednesday, three days after she disappeared.

There are, of course, many risks with free diving.

Firstly, there is the pressure of the water which builds as a diver descends further into the water. There is also the issue of temperature, as the deeper you go the colder the water becomes, which can impact even experienced divers due to the risk of cold water shock, which can cause muscles to freeze up.