The Mermaid Chair is a 2006 television film.
This movie isn't specifically about mermaids, it however features them heavily. The mermaids were played by three actors: Roberta Cenedese, Ananda Escudero, and Mandy-Rae Cruikshank.
A married woman, Jessie Sullivan, return to her childhood town to take care of her mother, while there she falls in love with a monk.
Jessie grew up with tales of mermaids by her father. One of which was about Mermaid Senora. Senora was also drawn to a monk. One day Senora was swimming as a human towards the monastery. Senora had left her tail behind, and an abbot found the tail and hid it. Senora was now stuck as a human and couldn't return to the sea. Senora eventually became a saint named Senara.
While Jessie Sullivan fell for the monk, she thought herself to be like the mermaid from the stories, tempting a monk.