"First, from head to toe, the head needs to stay in the axis, just like for any discipline, to reduce the drag but also to have the neck and the spine relaxed. It's really important because if they are tense, the rest of the body is tense. Now, the arms need to stay in the tube as you pull on the rope, so instead of going on the side you want to go in front of you, grab the rope as high as possible and if you want to grab the rope as high as possible, you need to be very close to the line, otherwise you will have an angle and you cannot grab as high as you want. The hips, they should be slightly forward, so that you keep your legs in check, because your legs need to stay in the tube and if you stay too relaxed in the hips and in the legs they are going to bounce around and then you are going to create a lot of resistance. So, it is better to use a little bit of energy to keep your legs and your hips in check and stay in the tube.
And finally the ankles. Because in free immersion you don't get to wear fins,if your ankles are a bit too loose, they will create a lot of resistance in the water and also that might mess up a bit your free fall. So the idea is to work on your ankle flexibility on a regular basis so that you can keep your legs straight, or close to straight, without using too much energy. If you're not very flexible in the ankles, i would still suggest that you point them a little, it takes a bit of energy but you gain so much efficiency and energy during your free fall".