According to religious texts, Lord Vishnu assisted in a sea churning with the incarnation of kurma (turtle). Kurma incarnation of Lord Vishnu is also called tachavav incarnation.
The story is as follows: Once Maharishi Durvas cursed King Indra of the gods and cursed them. When Indra went to Lord Vishnu, they asked to churn the ocean. Then Indra got ready to churn the sea together with the gods and the gods, according to Lord Vishnu’s saying.
Mathani and Nagraj Vasuki were made the leader of the Mandarachal mountain to churn the sea. The gods and the demons forgot their differences, uprooted Mandarachal and led them towards the sea, but they could not take it far enough. Then Lord Vishnu placed Mandarachal on the beach. Devata and the demons made Nagaraj Vasukhi the leader by putting Mandarachal into the sea.
But because there was no basis under Mandarachal, he started drowning in the sea. By seeing this, Lord Vishnu became the giant Kuram (turtle) and became the basis of Mandarachal in the sea.
Mandaracha started moving fast on the huge back of Lord Curum and thus the sea churning was completed.
“Om Namo Narayanaya. Om Namo Bhagavate Vasudevaya”