Nymphs are a race of female nature spirits that tend to take on a form related to their environment (Example: While in forests: trees, in flower fields: flowers, in bodies of water: water). They can take on a human form with brown, orange, blue, green or aqua skin color. In the animated series a nymph named Syrinx has a family of male tree-like entities, if these creatures are male nymphs or not is never explained; these "males" can only take on a partially humanoid form (resembling trees or bushes with faces). The nymphs reside on Phil's Island and Philoctetes enjoys spending his time peeping on the females.
A female tree nymph who resides on Phil's Island. Unlike the rest of the nymphs she apparently enjoys Phil's company and seems to be in a relationship with him. However, she was upset with Phil when he forbid Hercules from dancing (considering it "un-manly"). She tells him he's just as stubborn and hard-headed as her father, who disapproves of her relationship with a satyr. She appeared in Hercules and the Muse of Dance.
Syrinx's family includes her father and three brothers. None of them are happy with her dating a satyr, especially not her father. Their attitudes changed when Phil saved her from a fire her father caused.
In Hercules and the River Styx. Styx is technically a Naiad, or fresh-water nymph.
In the original myth, nymphs were a female-only species.
If Phil's Island is Rhodes where the nymphs live then, the water nymph in the film could possibly be Rhode (daughter of Poseidon).