When I swim in cool water, I usually find myself spinning my arm very quickly, which can't be done for long time in warm water (I will overheat at that kind of speed), And the stroke length is also reduced, resulting in roughly same speed as in warm water.

I was doing around 18 - 20 spl in a 25 m pool at the beginning, and 22 - 24 at the end of a workout, with around 55 stroke per minute last year when the weather was warmer, but now I am doing around 23 - 25 spl at the beginning, and 28 - 30 at the end of a workout, with around 71 strokes per minute. The workouts only consist of short intervals.

However, spinning my arms so quickly makes me exhausted.

When the water was warmer, I was experimenting my strokes per minute, but I couldn't put it over 57 - 60 without exhausting myself and/or sacrificing stroke length.