Siobhan-Marie O’Connor was born in Bath on 29 November 1995.
She fell in love with swimming at primary school and, in a rapid rise even by her sport’s standards, made the British team for the 2011 World Championships in Shanghai as a 15-year-old.
Having mentally prepared to join the queue for tickets for the Aquatics Centre at London 2012, a place at the Games was suddenly possible.
Nothing could have prepared Siobhan-Marie for the year that followed. While fighting through a chronic, undiagnosed condition and juggling intense training with GCSE exams, she qualified for London 2012 in the 100m breaststroke despite missing out on a place in her favoured 200m individual medley.
However just six weeks after the Games, Siobhan-Marie was diagnosed with ulcerative colitis - a long-term bowel condition that she would have to manage in the build-up to Rio 2016.
And, four years after diagnosis, she won Olympic silver in the 200m individual medley, Britain’s first-ever medal in the event.
In the latest of our series on TeamGB.com, Siobhan-Marie writes a letter to her 16-year-old self in the final days of 2011.
I’m going to level with you - I don’t know how you’re coping. I really don’t.
You can’t make it through a session without having to run and go to the toilet. You wake up and can’t see anything for 20 minutes because your vision’s so bad. You can’t really eat.
But, god, you’re just so determined, so completely fearless. So naive.
That all goes back to primary school. Remember how much you hated it? Remember how lonely it was, and how much you wanted to go home?
Swimming gave you this whole new friendship group and so much confidence. It was another life, away from school, and you found something you love and are good at.
The pool will always be your safe place. Yes, there will always be love, there will always be hate - but you will always be able to get in, switch the world off and pour your heart into it.
Deep down, it’s your everything and has been your life since you were ten.
You’ll take yourself to hell and back trying to make the London Olympics, but it’s worth it. You realise a lifelong dream, and you’ll never regret being true to yourself and chasing that.
You prove that mind can rule matter. You’ll want to go home and cry after missing out in the medley but Dave (McNulty, coach) and your family tell you: ‘get back on the horse.’
That’s what sport’s about. You pick yourself up, get back in the pool the next day and that gives you the confidence to drop a second - a second! - in the breaststroke weeks later.
London 2012 is magical. It ignites something in you. You get front row seats every night to watch the best swimmers in the world. That will be a crazy experience and crazy exposure to the sport.
Not long after, you’ll be told you’ve got something called ulcerative colitis. That’s what this is. But you’re going to spend the year after in denial and swim badly as a result.
You'll need to accept this is what you've got because you'll be in dreamland. There's no point ignoring it and trying to soldier on. It works for London 2012 - next time, it won’t.
You must listen to your body. You burn the candle at both ends and try to train flat out with terrible symptoms but you need to be smart and listen to Dave.
You’ll feel like your body is letting you down - and that’s going to be a constant battle. You’ll feel that five years later too and it’s a horrible way to be. You can’t hate your body, acceptance is the only way.
It’s easy to get frustrated, but it won’t stop you from achieving your goals. You’ll have to pull out of competitions and you’ll come close to stepping away, but your day will come.
Leading up to Rio, you’ll learn so many tough lessons and they will help it come together in what you've always wanted, your perfect race.
There's not one sportsperson you know who's had a completely smooth journey and that's what makes sport so great.
Nothing's guaranteed, and the best athletes are the ones who can pick themselves up and dust themselves off. And, believe me, you're one of them.