Just watch that over and over. That kid took 27 strokes per 50m for 1450m of the 1500m. That is unreal. I actually cannot fathom how economical that is. He looks to hardly be moving but he is swimming 58 seconds per 100 meters. On an efficiency level, Grant Hackett, the previous world record holder, was 31 stroked per 50 meters. This kid is about 15% more efficient. On a world level, that is HUGE.

If you doubt the effect of efficiency, stop. If you doubt economy of movement, stop it.

Believe.

Practise form again and again. Every swim. Every ride. Every run.