If you are a nationally ranked swimmer, are you a recruited athlete? If so, ask the coaches for help in what to include and what to exclude on the apps.
Did you take up swimming to help with asthma? That would make a good essay, how you used swimming to help your health condition.
No AO is going to read an application and say "Oh, if only covid hadn’t switched the international swimming competitions around this student would have taken the exams at a different time and gotten much better grades. " They aren’t going to infer better grades or give you credit for them when they weren’t earned. The teachers didn’t give you higher grades because of the circumstances and the AOs aren’t going to either. It is what it is.
There are plenty of colleges with swim teams that will admit you with the grades you have. Concentrate on those.