Kurma-Second incarnation of Vishnu

After Matsya form, Vishnu incarnated in the form of Kurrma (tortoise form) so that churning of ocean takes place and nectar of immortality can be extracted for DEVAS (God). According to ancient Puranas, Durvasa was a sage who was bad tempered. Once he was wandering the earth, he saw a Nymph of air and she was wearing a floral wreath. Durvasa demanded floral wreath from Nymph. Nymph gave it to him respectfully. Wandering further Durvasa encountered Indra(king of God) who was riding on his Elephant. Durvasa throws floral wreath towards Indra as a blessing. Indra accepted it and put it on his Elephant. Irritated by the fragrance of floral wreath Elephant quickly throws the wreath on the ground. Seeing this Durvasa felt disrespected and got very angry so he cursed Indra that he and his God's powers will diminish and they will become weaker. Demon king Mahabali saw this opportunity and attacked the Gods. Gods flew away from Demons and seek the assistance from Vishnu. Vishnu told Gods to call a truce with Demons and prepare to extract the nectar of immortality from churning of the ocean. Gods did as they were told. Churning of ocean required a lot of strength and Gods were weak so they asked for help from Demons and in return they will share the nectar with the Demons. Demons agreed on this. But the ocean body was so large that it requires Mount Mandara as a churning pole and Serpent king Vasuki as a churning rope.
As God and Demons started churning the ocean, Mount Mandar begun to sink due to its own weight.Then Vishnu incarnated in the form of Kurma and supported the the Mount on his back from beneath. As the nectar of immortality emerged with other divine things,  Demons took the nectar and begun to quarrel among themselves. So Vishnu took a form of beautiful women which mesmerized the Demons with its beauty. Vishnu fooled the Demons and retrieve the nectar. Vishnu distributed the nectar among Gods. Gods regained there powers. As soon as Demon discovered this trick it was too late. God defeated the Demons with regained strength.

Depiction of Kurma

The Kurma form is often depicted as upper human half with lower half of a tortoise.

Churning of milk ocean

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