When the milk ocean is churned, Lakshmi rises from it with a brightness that outshines lightning, and gods, demons and sages alike long for her. She is not to be won; she chooses. Walking among them with a garland she considers each in turn — one has austerity but no control over anger, one has knowledge but no detachment, one has power but no freedom from time — and passes on. Only Vishnu, who depends on nothing and lacks nothing, satisfies her, and she places the garland on him and makes his chest her home. Sri Vaishnava theology takes the scene as the reason the two are never separate.
A strand of Puranic and Bengali tradition, repeated by the World History Encyclopedia, gives Vishnu three wives: Lakshmi, Saraswati and Ganga. In the story the quarrelling of the three ends with Saraswati given to Brahma and Ganga to Shiva, leaving Lakshmi alone with Vishnu.
What is different here:
Adds Saraswati and Ganga as co-wives; the mainstream Vaishnava position knows Lakshmi alone.
Before she is a person Shri is a quality: the Rigveda uses the word for splendour and success, and the Shri Sukta appended to the fifth book calls on her as a golden goddess riding a chariot. The Shatapatha Brahmana gives her a birth from Prajapati as a shining, shaking woman whom the gods at once try to rob of her gifts. The Pancharatra's Lakshmi Tantra later makes her Vishnu's own creative power.
What is different here:
No churning and no choice of husband; Shri is an abstraction turned goddess, born from Prajapati rather than the sea.