This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Naiad (Greek)
In Greek mythology, the naiads are a type of female spirit, or nymph, presiding over fountains, wells, springs, streams, brooks and other bodies of fresh water. Naiads were often the object of archaic local cults, worshipped as essential to humans.
Boys and girls at coming-of-age ceremonies dedicated their childish locks to the local naiad of the spring. In places like Lerna their waters' ritual cleansings were credited with magical medical properties. Naiads could be dangerous: Hylas of the Argo’s crew was lost when he was taken by naiads fascinated by his beauty.