Swimming in UCSD pool, I started to count laps like in running, by rounds, to make it easier. So now, I touch the lap button on my watch on the start point only. I mostly swim a mile or so, in breaststroke, almost daily. Today I made 33 rounds (50 yards or 45.7 meters each, 25-yard laps x 66). It is 1650 yards, or ~ 0.94 miles, or ~1509 kilometers.
My times stopped improving: the time for 1.5K on the watch is one of my best times - 41 minutes and 14 seconds, often I am 1-2 minutes slower.