The rotation of the body is easy to do, but many people don’t know that there is a short pause in the rotation. This pause makes you swim way faster.
The energy transfer between arms and legs is what makes you move well in the water. It doesn't matter if you use your legs a lot or a little.
Many call that transfer of energy body rotation. But if you look at it in detail, the whole body doesn’t rotate at the same time or to the same degree. Doing that is a big mistake.
 
Follow this video series in order:
1- Swim with LESS Effort:   

 • Swim with LESS Ef...  
2- Is it really easier to kick less?:   

 • Is it really easi...  
3- The Most Important Body Part In Swimming:   

 • The Most Importan...  

00:00 - The rotation of the Torso
00:24 - Muscles and bones when swimming
01:02 - Hips and Shoulders
01:46 - Aaron getting ready to swim in an ironman triathlon
02:48 - Drills to improve the rotation
05:43 - Dry-land exercises to improve swimming