Plavini has originated from the Sanskrit word PLU that means to float. Thus Plavini means the one that causes to float.
The student actually drinks air like water slowly and sends it to the stomach. The stomach gets bloated a bit. If you tap the stomach when it is filled with air, you will get a peculiar tympanic (air) sound.

Method for Plavini Pranayama:

Plavini is not so much a breathing technique for getting air into the lungs as an air-swallowing technique for getting air into the belly.
In the beginning practice this Padmasana, Siddhasana or Vajrasana. With practice you can perform it in standing or lying posture as well. If you are performing it in sitting posture, inhale the breath through both the nostrils and retain it by Jallundharbandha. When you take Jallundharbandha, the retained air fills the intestines, which get inflated as a result. End the Pranayama with exhaling the breath through both the nostrils. If necessary, remove the air that is trapped in the intestines by balancing or Uddiyanabandha.
 

    Benefits of Plavini Pranayama :

    Expert of Plavini Pranayama can sustain his life for many days without food.

    During the practice of this Pranayama the blood flows in the body extremely speedily

    thus removing the impurities and toxins accumulated in the body.

    With practice of this Pranayama, the performer gains the power to float on the water.

    An expert can even remain floating on deluging waters like a light lotus leaf.

Note :

For the perfection of this Pranayama, slow but continuous and regular practice is extremely essential. Hence practice is extremely essential. Hence practice this Pranayama in the guidance of an expert teacher only.

Essential of  Pranayama

KINDS OF PRANAYAMA
Pranayama is Practice only after purifying Nadis

Nadi Shodhan Pranayama

KapalBhati (Glowing of Skull)
 Among the many kinds of Pranayama. i.e. Kumbhaka, eight kinds are considered as main. These are

Surya Bhedan Pranayama,

Ujjayi Pranayama,

Sitkari Pranayama,

Shitali Pranayama,

Bhastrika Pranayama,

Bhramani Pranayama,
Murchha Pranayama and

Plavini Pranayama

Also read from Kundalini Yoga-SRI SWAMI SIVANANDA