Funny answers. **I count lengths, not laps, and I repeat the length I’m on with each stroke. “1,1,1,1,1,1,1,1 flip turn, 2.2.2.2.2.2.2.2, **etc.”
(insert side thread on merits of flip turns here).
I find the monotony of repeating the length count in my mind counters the monotony of the black line on the bottom of the pool and I enter a state of harmonic convergence. Plus, I feel like it helps me keep my turnover rate consistent, as I count with the strokes and get into a rhythm. Just don’t count sevens in your head, as that’s two syllables and you’ll slow down. And then adjust for 11 and higher.
Never mind. I lose count too. Go by the timer.
+1. Counting single lengths is superior because you get an immediate “audit” after every turn, as odds/evens are always facing in opposite directions ~ so you should easily be able to catch your error within one length and then it’s usually easier to tell at that point whether you should be on 15 vs 17, for example, whereas If you’re counting 1 ‘lap’ as a round-trip then it’s less clear whether you’re on lap 7 or 8 because there’s no directional cue to help you figure out how long ago you lost track so it’s easier to zone out longer before becoming aware of it.
For any interval workouts, the longest I’ll ever do is 400 anyway, so sometimes I can think of it as 2-200s if there’s something like varying breathing to break it down like others have mentioned, as opposed to counting straight to 16. And for the occasional once or twice per season 1650 (indoors) or 2K/3K (outdoors), I’ll break it into 500s so I only ever count up to 20 before starting over.