That was “fun”, in the sense of “Oh, I haven’t done that in a while, and it was harder than I expected.”
Looks like 17:37 for the 1000 meters - that’s in a 50m pool, using flip turns. At the moment I probably couldn’t do it much faster - I deliberately tried to go a touch slower at the start, because I haven’t done 1000m straight through in a long while, and my arms were close to wiped out at the end. Based on how tired I was, I paced it better than I would have expected. The Apple Watch tells me average 1m45s for 100m / 52s for 50m; the 100m splits ranged from 1:39 to 1:50, which I guess is moderately consistent. Those times are about typical for me: I find 55s for 50m is “I’m exercising, but not pushing myself”, and 50s is “I won’t be able to do this for long!” That range has been steady for many years for me.
Doing 1000m was an odd little cognitive flip. I usually put in kick lengths to make sure my legs are doing something - which means I forget how my arms are getting a break, apparently more significant of a break than I realized!
Gah, now I’m perhaps foolishly wondering how to improve that time, or if I want to try … I haven’t done training sets since I was on a team as a teen in the 80s; never on my own.