A Water Faerie (Undine, Water Nymph, Water Spirit) arises from the ocean on a wave wearing a crown of pearls and surrounded by shells.
In Greek mythology she is called a Nereid.
Water Faeries also inhabit waterfalls, lakes and streams. An Undine or Water Elemental can gain a soul if she marries a mortal and gives birth to his child. But if he is unfaithful, she returns to the sea.