Without being big headed, i'd say that swimming is one of the few things i'd consider myself more than just "ok" or even "good" at. I've always been very good at it.
However, from the age of say 14-19 i didn't swim properly at all (properly being training, competing etc). I'd just go to the local pool & dick about like everyone else, so i lost some 'edge'.
Then i got back into it again in my early 20s. I was going quite regular & building up my stamina.
After some time, my stamina surely improved, and i was much stronger than the 10-12 year old lad i was when i was competing, yet i found something odd.
I felt like i was nowhere near as fast as i was when i was 10-12, even though i was obviously stronger.
Another thing was, i remember banging out lap after lap as a kid. I can't remember the time frame we had for it, but i banged out 60 laps & wasn't even tired, just to attain some distance badge.
When i was into it in my early 20s again, i was fine for a couple laps, but then i tired massively.
Chances are there's only the casual swimmer on here, but i thought i'd put it out there to see if anyone shared a similar issue & how you could work round it, or have any idea on how you'd work around it, as i'd like to get back into it more again.