Why I love swimming in green water

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    A 2nd Olympic pool in Rio turns green

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A 2nd Olympic pool in Rio turns green 01:12

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  • Swimming writer Joe Minihane says emerald water is an invitation to dive in
  • Out in nature, green water means freedom to explore, he says

(CNN)Stand me at the top of a 10 meter diving platform and the swirl of vertigo will be enough to send me clambering nervously back down down the narrow steps.

But once I get to the bottom and my legs are no longer jelly, you'll have no problem getting me into the water for a few quick laps.
    Especially if the water's a deep shade of green.
    Rio's Olympic diving competition won't be remembered for Britain's first ever gold medal in the springboard, or Chinese domination from the very highest platform.
    Rather, it'll be the fact that the pool into which fearless Olympians have been diving has gone from a sparkling blue to a mysterious emerald.
    Organizers won't give a reason for the change, except to say that it's no risk to the health of competitors.
    Even so, British superstar diver Tom Daley tweeted that the pool was closed for training on Friday, without an explanation from Rio 2016 staff.
    Obvious health concerns aside, I think it looks pretty alluring.
    Don't get me wrong, I'm not about to board a jet to Brazil just take a dip in a pool that's clearly not the color it's meant to be. But there's something about green, murky water that sets off an urge in me to strip down and dive in.

    Swimming with the birds

    Green water means freedom to explore.
    It doesn't matter what it is. Green sea, a dark lake, a quietly meandering river. If it's warm outside and there's an easy way into the water, I want to get in.
    My obsession began at London's Hampstead Mixed Pond six summers ago.
    Open from May to September, this oasis of calm just north of the city center is tended by lifeguards but has a pleasingly rustic feel. Basic changing sheds, a short concrete jetty and 80 meters of deep water beneath which lurk pike, perch and assorted amphibians.
    It's not just slimy creatures though.
    A vast array of birdlife lives around its edges and on its surface. Moorhens, coots and great crested grebes to name a few. When I get into the pond, I feel as if I have become part of nature.
    Walk along the bank of a river or lake and birds will scatter, fish will dart off. Once you're in the water, you're one of them. I've swum alongside birds happily tending to their young and been scooted around by fish as they luxuriate in refracted sunlight.
    I love an open-air pool or lido, but you just don't get this feeling when you're powering out lengths in them. They're for more serious swimming.
    Green water means freedom to explore, to wander in your most uneven breaststroke, without fear of being overtaken by a triathlete in training.
    It's not just spending time with nature that makes green water so appealing. It's a whole new way to see the landscape.
    I spent two and a half years retracing "Waterlog," the seminal 1999 travel book by Roger Deakin, which saw the late English naturalist indulge in a "swimmer's journey through Britain."
    "Through" is the operative word. Deakin was all about "being in the scene."
    When you're in the green water of a river or pond, you get angles and views that are not possible from dry land.
    I have been buoyed up in high drainage channels on eastern England's Norfolk Fens, unable to see the vast fields around me, the sky an impossible dome.
    I've stared up at brooding mountains from the gloomy bays of Jura on the west coast of Scotland.

    A guide to the murky depths

    River research: Fresh water swims take some planning.
    I've peered through goggles at the swaying tresses of a sea kelp forest off a remote beach of the Isles of Scilly.
    Only glorious green water has afforded me such opportunities.
    There's the calmness that comes from being in a river, bay or pond too. Your body is focused solely on survival. It's impossible not to be in the moment.
    Following Deakin, seeing the world through the green tinge of the lakes, ponds and rivers he visited, helped ease problems with anxiety that I've suffered from for much of my life.
    It's not a catch-all cure, but when I am in wild, open water, I am present. It's something I've striven for on dry land, but it's a feeling I can only truly attain when I'm out swimming.
    Of course, there's a need for caution when entering the murky depths.
    It's not advisable to swim alone, any stretch of water needs to be researched before being swum in and quarry pools should be avoided because sudden drops in depth can lead to freezing temperatures.
    Only stay in for a few minutes at a time and don't get cocky. Open water swimming takes months for the body to attune to and there are no medals for who can stay in the longest.
    If these simple rules are followed, the pleasures of green, mysterious water can be anyone's.
    The luminous shade of the diving pool in Rio might not look too enticing, but try to see it as an inspiration to get out there and explore more natural bodies of water of a similar hue.
    I know I have.