A water spirit is a kind of supernatural being found in the folklore of many cultures:

African

Some water spirits in traditional African religion include:

• Mami Wata is a transcultural pantheon of water spirits and deities of the African diaspora. For the many names associated with Mami Wata spirits and goddess, see Names of Mami Wata.^[1]
• Owu Mmiri of some riverine people of Nigeria are often described as mermaid-like spirit of water.^[2]
• A jengu (plural miengu) is a water spirit in the traditional beliefs of the Sawa ethnic groups of Cameroon, particularly the Duala, Bakweri, and related Sawa peoples. Among the Bakweri, the name is liengu (plural: maengu).
• A simbi is a mermaid-like or reptilian spirits from Kongo tribe and related to Vaudou religion.

Celtic

In Celtic mythology:

• An Each uisge is a particularly dangerous "water horse" supposed to be found in Scotland;^[3] its Irish counterpart is the Aughisky.
• The Gwragedd Annwn are female Welsh lake fairies of great beauty.
• A Kelpie is a less dangerous sort of water horse. There are many similar creatures by other names in the mythology including:
  • the tangie (Orkney and Shetland)
  • the nuggle also known as the shoopiltee or njogel (Shetland)
  • the cabbyl-ushtey (Isle of Man)
  • the Ceffyl Dŵr (Wales)
  • the capaill uisce or the glashtin (Ireland)
• Morgens, Morgans or Mari-Morgans are Welsh and Breton water spirits that drown men.
• Selkie

Germanic

In Germanic mythology:

• The Nixie (English) or the Nix/Nixe/Nyx (German) are shapeshifting water spirits who usually appear in human, or horse, form
• The Undine or Ondine is a female water elemental (first appearing the alchemical works of Paracelsus)
• Jenny Greenteeth in the folklore of Lancashire
• Peg Powler said to inhabit the River Tees in Yorkshire
• The grindylow in the folklore of both Lancashire and Yorkshire.

Ancient Greek

In Greek mythology:

• Naiads were nymphs who presided over fountains, wells, springs, streams, and brooks
  • Crinaeae (Κρηναῖαι) were a type of nymph associated with fountains
  • Limnades or Leimenides (Λιμνάδες / Λειμενίδες) were a type of naiad living in freshwater lakes.
  • Pegaeae (Πηγαῖαι) were a type of naiad that lived in springs.
• Nereids were sea nymphs.
• Sirens were bird-bodied women living in the sea near a rocky island coastline.

Japanese

In Japanese folklore:

• Kappa (河童, "river-child"), alternately called Kawatarō (川太郎, "river-boy") or Kawako (川子, "river-child"), are a type of water sprite.
• A Hyōsube (ひょうすべ) is a hair-covered version of a Kappa.

Mesoamerican

In Aztec belief:

• Ahuizotl; a dog-like aquatic creature that drowned the unwary.

Oceanic

In the mythology of Oceania:

• Adaro were malevolent merman-like sea spirits found in the mythology of the Solomon Islands.

Roman

In Roman mythology:

• Camenae were goddesses of springs, wells and fountains, or water nymphs of Venus (mythology).

Slavic

In Slavic mythology:

• A Vodyanoy (also wodnik, vodník, vodnik, vodenjak) is a male water spirit akin to the Germanic Neck.
• A Rusalka (plural: rusalki) was a female ghost, water nymph, succubus or mermaid-like demon that dwelled in a waterway.
• А Berehynia in ancient Ukrainian folklore is a goddess spirit that guarded the edges of waterways, while today it is used as a symbol for Ukrainian nationalism.
• Moryana is a giant sea spirit from Russian folklore.
• For potoplenyk, vila/wila/wili/veela, and vodianyk, see also Slavic fairies.

Thai

• Phi Phraya (ผีพราย, พรายน้ำ), a ghost living in the water.
• Phi Thale (ผีทะเล), a spirit of the sea. It manifests itself in different ways, one of them being St. Elmo's fire, among other uncanny phenomenons experienced by sailors and fishermen while on boats.