Lord Vishnu is married to Lakhsmiji . After marriage he preferred to stay with goddess Lakshmiji in the Sea . The Sea is considered as Father of Lakshmiji.
So what made lord Vishnu stay in the sea?
May be your are referring to Lord Vishnu's leela about the Nachiyar Koil . You can read more about the temple and the preciding deities. It is said that the Lord appeared in Venkateshwara form to marry Lakhsmi, but as demanded by Lakshmi the Lord should stay with Her and not the opposite where the bride goes to the husband's house. Probably this question will further answer your doubt.