She missed out on a place in the final, finishing 6th in her semi-final in 1:57.56, joint 13th overall, but can count herself as one of the fastest 16 swimmers in the world – and will surely be back and approaching her peak at Tokyo 2020.

WATCH: relive the action involving Hong Kong athletes on Day 3 at the Rio Olympics

“At first I wanted to get to the semi-finals – then Fina released their psych sheet and I was ranked 28th,” said Haughey, who had shattered her own Hong Kong record earlier in the day in the heats with 1:56.91.

“I told my coach, ‘That seems a bit impossible!’ But he told me, ‘They’re just times, try your best,’ and being able to swim in a semi-final for Hong Kong, I’m just very happy and honoured.”

Hong Kong’s only previous Olympic swim semi-finalist was Cheung Kin-man at Helsinki in 1952, when the sport, and the Games, were very, very different.

WATCH: golden moments on Day 3 at Rio Olympics

After qualifying in terrific fashion in the afternoon, Haughey scratched from the 200m individual medley to conserve energy for the night-time semi. It was surely the longest eight hours or so of her life, and not just because her phone was blowing up and she couldn’t look at it – any 18-year-old’s worst nightmare.

“In the past two or three days I’ve been trying to stay away from social media, I wasn’t on Facebook or Instagram or WhatsApp or anything, but I keep getting notifications on my phone – I think I have 150 Facebook notifications I’m still waiting to check, I just didn’t want to be distracted by anything.”

Haughey was watched by her family, plus her University of Michigan roommate and her mum and dad.

Her college coach was also at the pool, though Mike Bottom was likely preoccupied with another UMich ‘Wolverine’, Michael Phelps, in his role as the US team’s assistant coach.

Despite the magnitude of the occasion, Haughey seemed nerveless and was second fastest off the blocks.

“Before I left the US to come here I was really nervous, but my coach in Michigan he told me, ‘You know, it’s just another competition, it’s the same 50m pool, you’re racing the same people just like the World Champs or NCAAs so that kind of calmed me.

“I tried not to think ‘it’s the Olympics’, just another swim meet.

“I’m sure [Bottom] will be around the pool – after my 200 free I saw him and his eyes were red, he’s a very emotional person and definitely happy for me.”

WATCH: teenage swimming star Siobhan Haughey gets ready for her debut in the Olympics

Haughey’s heat time would almost have been enough to make the final – Barratt Bronte of Australia was eighth overall in 1:56.63 – to underline how close she is to the main event.

“I was kind of shocked, I touched the wall, turned over, took my googles off and saw the time, I was like ‘1:56 that shouldn’t be my time!’

“I had to look again and realise that was actually my time I never thought I could swim that fast.

“I could go a lot faster but [Tokyo] is four years later and that’s a very long time away. I’ll definitely take a short break after the Olympics talk to my coach and see what the plan is in the next few years and see how we can improve and get to my goals.”

Despite the social media blackout, some of the bemused comments floating around the blogosphere – ‘a Hong Kong swimmer called Siobhan Bernadette Haughey??’ and the like - did make it to her courtesy of amused friends.

Haughey’s dad is Irish and mum is from Hong Kong. Born and raised in the city, the former St Paul’s Secondary school student revealed that the land of her father had been in touch to sign her up, but it was never an option for the swimmer sporting Bauhinia and Olympic rings nail polish she had done in the Athletes’ Village.

“I saw some of it – I find them very funny,” she added. “I’m happy that I could represent Hong Kong, I could represent Ireland because my dad was born there, but I was born in Hong Kong and I feel connected to Hong Kong and I’m proud of representing Hong Kong.”