Sitting beside a woman in Bangladesh, watching the tears roll down her cheeks I searched for some words of comfort.

But none came.

This bereaved mother, Hosna, was bravely recalling the day that her 11-year-old son, Emamul drowned in front of her very eyes. He was just playing beside a calm and still river bank when he fell in. He had no idea how to swim so, within minutes, he was gone.

"When I think of him, my heart breaks", she explains.

It goes without saying that Hosna's story is devastating. No mother should have to face the death of their child. But what I found most difficult to comprehend is that she's just one of 50 grieving mums who lose a child in this way every single day across Bangladesh alone.

Learning to swim in the UK is something that most of us take for granted. Like learning to ride a bike or how to read and write, it's one of those life skills that nearly all of us are taught in our early childhood. But in Bangladesh, where I'd come with Sport Relief to see how the money they raise changes lives, I realised that teaching children to swim just isn't possible when every day is a struggle to get by.

Poor families spend every waking hour doing what they can to make ends meet and they don't have the money spare to pay for swimming lessons. And since they weren't taught to swim themselves, they can't then pass this vital skill onto their children when the time comes. It's a vicious cycle that has disastrous consequences.

In Bangladesh, the monsoon season combined with unpredictable storms brought about by climate change leads to severe flooding where whole lives get washed away. Knowing how to swim isn't a luxury, it's a matter of life and death.

That's why Sport Relief is funding an incredible project called The Monhorhardi Swim Safe Project that not only teaches children how to swim, but also teaches them how to save others in the water too. And the cost of such a vital scheme? Just £5 per child.

My wife Danielle and I felt hugely privileged to see this project in action as we accompanied Hosna and her six-year-old son Imdab to his very first swimming lesson.

Since losing Emamul, Hosna has been petrified that her younger son would face the same dreadful fate. But watching her little boy tentatively get into the water for the first time in his life, a smile appeared on her face and her tears weren't those of sadness but of gratitude. Thanks to Sport Relief, she no longer needs to be afraid.

Already this year, hundreds of thousands of people have gone to great lengths to support Sport Relief 2012 and even more will be doing just that on the weekend of the 27 - 29 April as they take part in the Big Splash Mile for Sport Relief at local swimming pools up and down the UK.

You can find out whether your local pool is taking part by going to www.swimathon.org, and having seen what I've seen, I really hope that everyone who can take on the challenge will do just that.

Swimming a mile may sound like a lot, but the very fact that so many of us can swim at all is something that we should never take for granted. So diving in to stop children from drowning seems like a truly fitting way to support the cause and stop mothers like Hosna feeling such pain again.

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