https://www.swim-central.uk/what-age-should-children-learn-to-swim/
In England, swimming becomes a part of the national curriculum around Year 3 or 4.
https://en.wikipedia.org/wiki/Year_1_(education)
Year 1 is an educational year group in schools in many countries including England, Wales, Australia and New Zealand. It is usually the first year of compulsory education and incorporates students aged between five and seven.
Hmm. So she probably should have had swimming instruction by that age.
Could try running it under mangohud. Dunno if that indicates the renderer being used, but I'd guess that it likely does, and would let you test that theory.
One Windows user here had some problem with very low FPS in the game, and found that limiting FPS in the Nvidia software resolved it. I'm suppose that it's not impossible that it's some bug in the game that you're also tripping.