Last year saw the 17-year-old Bishopbriggs Academy pupil enjoy a series of major swimming breakthroughs, including winning six European Championship medals, two of them gold.
She also earned a call-up to compete for London Roar in the prestigious International Swimming League and, last month, reached a final in her first ever World Championships appearance.
But far from resting on her laurels, Shanahan is already looking forward to a 2022 programme which not only includes World and European Championships but also the Commonwealth Games.
And she says is looking to benefit from the experience of being part of a London Roar team which got to the final of the ISL.
“It was such a good experience, especially because I'm so young." she said.
"It was my first ISL and I've met so many new friends in the process and really enjoyed racing everyone from all the different teams around the world.
"You never really get to experience being on a team with other nationalities, it's always just your country.
"It's a very different aspect that's been brought into swimming and you're not just competing with them, you're training with them, spending every day with them and finding out about their cultures, the different ways that they train and their different views on swimming. It was really interesting."
Shanahan admits the progress she had made in 2021 has probably exceeded any expectations she had at the start of the year.
But it has also raised the bar for 2022, with her targets including gaining selection for the World Championships in Japan in May and Commonwealth Games in Birmingham in July, the trials for which are in Sheffield in April, first on the horizon.
“Coming into this year it was a bit all over the place with lockdown at the start and not being able to do any competitions or train anywhere,” she said.
"For a lot of people, it was unexpected what the year was going to be so to swim the way I did – I'm really proud of myself.
"I just want to improve and keep going as I am.”