I was a competitive swimmer in high school, and I note that the Olympic lap times are about on a par with mine.
Except that they're in a 50 meter pool, and I was in a 25 meter pool.
At one point I could run marathons in 3 hours, 50% longer than the winners. Now I'm old, and I'm trying to get back to running them merely 100% longer. That is unlikely.
It’s just unbelievable unless you’ve experienced it. At the absolute top of my game, on my best day, I would still be more than a boat length behind the Olympic guys on their off days.
I find some consoling symmetry in that I can run faster than the fastest swimmers and bike faster than the fastest runners. At least on some distances.