Your breath can be an amazing tool for calming the mind and relaxing the body. Try to breathe primarily from your nose. At first, you can consciously take deep breaths, but once you settle into your experience try less to manipulate the breath and more just observing the breath. Your body will always remember to breath, there is no need to control your breath.
The most important thing is to get comfortable. There are only two real positions in the tank:
With your arms are your side, palms down; Arms over-head with your palms up.
Play around with the two to see which feels better for your body. Also, try to position your body in the middle of the tank to avoid “ping-ponging” from side to side. To do this, brace your arms and legs against the sides of the tank to position your torso in the middle, and once you feel the water to be calm, slowly and evenly retract your limbs back to the midline of your body. Try not to generate any momentum from either side so that you remain in the middle and avoid the distraction of bumping into the side. Once you like your position and feel comfortable try to remain still and consciously relax all of your muscles.
Letting go (lack of effort)
Don’t “try” to do anything in the tank, don’t force something to happen, don’t expect something to happen; this is the exact opposite direction from where you may want to go while in the tank. You will not fall asleep necessarily, just be present. Repetition of a focus word such as “peace”, “relax”, or “let go” spoken in your mind in unison with your exhalation can help at first, but the message here is to just let go of conscious control.
Being physically still by finding a comfortable position and remaining there combines with still your mind either through breath awareness or a focus word (mantra) can lead you into a state of holistic sillness. This can generate the perception of timelessness, your state of being will be extremely relaxed and this is when the body is in a state of healing.
With external stimuli at a minimum, your nervous system will turn up the volume to try and sense anything, Since there is still “nothing” coming in, there is a great opportunity to simply sense whatever is left to be felt within your internal body. Feel your arms, legs, torso, head, as intensely as possible. Cultivate as much sensitivity to these parts as possible. Feel the energetic uniformed consistency of these parts and observe them without judgement, without limits. Observe your thoughts, emotions, and sensations.