Goddess of the sea - P. C. Cast

Home alone on the night of her twenty-fifth birthday, US Air Force sergeant Christine Canady yearns for something to cure her loneliness. After drinking too much champagne, she recites a divine invocation to revive her humdrum life. But how is she to know the spell actually works?

When her plane crashes into the ocean, CC's life changes forever. She awakens, bewildered, to find herself in a legendary time and place ruled by magic - and in the body of the mythical mermaid Undine. But danger lurks in the water, ready to swallow CC whole. Taking pity on her, the goddess Gaea turns CC into a damsel so that she might seek shelter on land. When a dashing knight comes to CC's rescue, instead of falling for this dream-come-true, she aches for the sea and the darkly sexy merman who's stolen her heart...