The first objective I have in swim practice is to bring my body and my mind into the water. The next objective is to bring my mind into my body. The third objective is to bring all my internal systems online and into a unified, cooperative state for higher performance. Then I am ready to work for the day.
If I cannot achieve this unified state within the normal time frame it usually indicates that I am fighting an illness and need to get out to rest for the day. Or it may be that I should remain in this Tune-Up process longer.
Silent Swimming is a very useful activity in Tune- Up (a.k.a. Warm Up) for accomplishing these objectives.
I recommend at least 8 minutes for this. 12 minutes is about minimum for myself.
Basically, the task is to produce as little noise, splash, bubbles (= lowest turbulence) as possible. It is not about moving slow, but rather it is about moving gently and that usually compels us to start slow and wait for the systems to unify and tell us when its time to turn things up. This is based on the premise that our bodies really do want to work hard and perform at highest capacity. The body has inbuilt wisdom for how to get there each day and a signal language through which it communicates that wisdom. We need to learn how to read those signals and respond cooperatively.
Silent Swimming is an exercise, or more so a discipline, in listening and responding to those signals.
In Silent Swimming you may start out gently and increase tempo as you feel your body relaxing, the joints loosening up, the tissues starting to slide and yield to a full range of motion. Blood will migrant to the areas of your body that need to work. Heart rate and respiration will increase and come into a working rhythm. Your attention to your nervous system and especially to the surface of your skin will awaken and focus. Energy production will turn up and urge you to use it.
Read more about this in the post Silent Swimming.