Kate Rusby learned this song from a Nic Jones record; he adapted it from a set published by Walter Scott, which is also in the thread MMario linked to.  She also recorded a song which she called The Drowned Lovers; this she also learned from a Nic Jones record.  There is a transcription made from Kate's record here:  The Drowned Lovers  and an older, traditional version here:  THE MOTHER'S MALISON (Clyde's Water)

Malcolm