It’s the reason I have an A3 along with my S9P blue titanium, to be able to have on point distance measurement for pool swim sessions, and if you add that you can teach the A3 how you swim each style, it made me pull the trigger on a less than 100 usd brand new A3P that was only a in-store shown watch here in Suunto México
Haven’t tried after latest firmware update for S9P, but last year A3P did a more real measurement of distance in Open water as well , S9P measured like 400 meter less