It wasn’t a priest it was Bo the daughter. It’s hinted at when Mel is telling her the story of how she was born. “You didn’t cry you were an angel” he meant angel metaphorically but unbeknownst to him she really was. Hence; the water was blessed.

Seems a lot of people hating the ending but I thought the movie was great one of my all time favorites. Mel Gibson and Joaquin Phoenix were both awesome in it and I loved how on the surface it was aliens but there’s a metaphor under it for faith. Loved it