Researching water nymphs

Pursuing my interest in all things mermaid, a book I’m keen to read by the acclaimed author of The Secret Life of Bees, Sue Monk Kidd, has a lovely take on the metaphors and literary possibilities of mythological mother/daughter relationships. See her interview with The Examiner.
Working on material on mermaids, sea myths, river spirits and the like. Loved image below for inspiration. Thoughts on especially marsh-related water spirits very welcome in “comments” below.