From ankle-deep mud in Central Asia to the scorching heat of Australia, Mina Guli is running 100 marathons in 100 days to highlight a looming global water shortage.
The 48-year-old Australian is galloping across the planet, 42km at a time, with barely a moment to adjust her watch before it's on to the next stop.
Her unorthodox world tour began in New York on November 4 and has so far taken in France, the Vatican, India and Hong Kong.
Guli, a former lawyer, will race through dozens more places - including in Jordan, Kenya and Mexico - before she gets back to New York on February 11 for a triumphant final marathon.
"Running is not my favourite thing in the world to do by any stretch of the imagination," Guli said.
But it has opened her a path to adventure - like in Uzbekistan where city streets were closed for her, she had a police escort and the mayor joined her for a jog.
"When you see all the traffic banked up at the traffic lights for you, you just think 'wow I need to be running faster or something'," she said.
Despite an itinerary that would be the envy of many a seasoned traveller, Guli and her six-strong support team have no time for tourism.
Often they bed down in tents and try each day to meet people either bearing the brunt of drought or working to save water.
Guli is chief executive of Hong Kong-based not-for-profit organisation Thirst, which works to highlight the pressures on the global water supply.
"We forget that water goes into everything we buy and consume every day," she says, including not just the food we eat, but all the clothes we wear.
And, say experts, as the planet's population increases, this precious resource will become ever-more scarce.
The UN estimates that, by 2030, demand for water will outstrip supply by 40%.
That thought, says Guli, is what keeps her going through the longest - and most difficult - slog of her life.
"So many things have gone wrong. So many times I've sat there in absolute exhaustion, unable to keep my eyes open, let alone stand up and walk in a straight line, let alone run a marathon," she said.
But a determination to fight for her chosen cause and improve life for younger generations gets her back on her feet.
"When... I think about the hopes and dreams of those kids I take my hands off my face, I stand up, I stop throwing myself a pity party and I continue running."