Jai Sriman Narayana !!
Srimad Bhagavatha Puranam describes the glories of Sri Kurma Avatar of Lord Vishnu which stands second in the well known ten incarnations of Lord Vishnu.
The deities and Lord Indra lost their glories due to the curse of Sage Durvasa. They became powerless and doomed into darkness. The demons used the opportunities appropriately and driven out the deities from the Heaven. All the deities approached Lord Brahma in Satya Loka. Lord Brahma instructed them and drawn them near to Lord Vishnu, to the Abode of Sri Hari.
Lord Vishnu inculcated that, to regain the lost powers of the deities and Lord Indra, is possible only with the divine nectar of Immortality. They decided to churn the Milky Ocean for the divine nectar using Mount Mandara as the center object and Vasuki who was the King of Serpents as rope. Lord Vishnu assured the deities that He would make sure of the things in such a way that the demons did not get a single portion of the divine nectar. Lord Brahma returned to Satya Loka.
As planned earlier the deities approached the Demon King Bali to inform the proposal of Chruning Milky Ocean. The arrival of deities and Lord Indra to their Kingdom made the demons furious. King Bali who was wise and Intelligent, controlled the situation thinking that the arrival of deities would do good for him. King Bali received the deities and Lord Indra with due respect and honor. Lord Indra explained the decision of Chruning Milky Ocean and requested to extend possible help from them. Lord Indra also informed them that this venture would definitely yield some benefit to them.
The deities and demons proceeded to Mount Mandara, while carrying Mount Mandara to the Milky Ocean, many of the deities and demons were gave up their lives. The whole process seemed to be the toughest and Lord Indra got disappointed. Soon Lord Vishnu appeared on His Celestial Vehicle - Garuda, with a mere glance at the dead turned alive. Later, Garuda carried Mount Mandara on His shoulder to the seashore.
The deities and demons started the process of churning the Milky Ocean keeping Mount Mandara as center object and Serpent Vasuki as the rope. Immediately, they realized that the Mount Mandara started sinking into the deep water, the process made much more difficult to continue. At once The Supreme Lord tuned into a huge tortoise and plunged into the Ocean. He graciously carried Mount Mandara on His back. The deities and demons resumed their work. Within a short while all were wearied and depressed as nothing was coming out from the sea. They continued churning; suddenly Halahala Poison was propelled out. The deities and demons were seriously affected by the smoke of the poison, they hurried to Lord Shiva. Lord Shiva effortlessly carried the poison in his palm and swallowed it. The deities and demons recommenced their work. While churning in progress, many precious things were came out such as Ucchaisravass -White Horse, Sri Mahalakshmi, Kaustuba - Precious Jwel, Airavatha - White Elephant, Rambha, Moon, Parijatha Tree, Surabhi, Conch and finally the Lord Dhanwanthari with Ambrosia - The divine nectar of Immortality.
Jai Sriman Narayana !!