Häll broke her Swedish record by 3.5 seconds, to 8:33.12, and advanced to Tuesday's final in the 800m freestyle with the fifth-fastest time.
Just 50 minutes after swimming the second leg of Sweden's 4x200m freestyle relay, in which Sweden was eliminated.
I went straight from there and swam, went to the tent and got some energy, both water and some candy, and then both the coaches from the USA and Martina (national team captain Aronsson) were there, so I had a big support team helping me, says the 21-year-old, who represents Elfsborg but swims in college in Kentucky, USA.
The explanation for the record-breaking performance?
I don't know... the tapping has finally worked, I've had a hard time with it over the years. Mainly mentally, I think. But it's something that has given me a lot in the US, it can feel like anything, but you just have to do it. There are no excuses, she says.
The final will be decided on Tuesday, and then Häll will not have to do double duty.
So there should be more to give.
"I have to look at my splits, fine-tune both tactics and how I swam. I've always said I'm a finals swimmer, so I'll have to prove it," she says.
What do you think?