Underwater yoga is an interesting challenge that should only be attempted with significant experience in Hatha yoga asana & pranayama or freediving. To sink to the bottom one needs to expel most of the air in the lungs. Practicing in a pool will be best to minimize movements from the water and the greater ease to sink. Practice with a friend for supervision and safety. The best positions to start with our at the end of this video. These are sitting in a tuck, and laying face down. Underwater yoga creates an environment suitable for pratayahara, or sense withdraw. This is a meditative state where your consciousness is totally focused on the simple actions of maintaining the position and much of the outside sounds and sights are blocked. You are really in a different world it feels like. All of the benefits of getting in the water are there too. And because you exhale completely to sink, the pressure on the torso and organs will be greater, causing a cleansing circulatory action for the lymph and digestive systems. Holding the breath out is also one of the best ways to control the mind. Simply pausing the breath out here and there throughout the day helps to relax your body and decrease mental anxiousness.