Perhaps the most important water-goddess from northern Britain was Coventina whose cult, like that of Sulis, was concentrated at one particular site, Carrawburgh, on Hadrian's Wall. Her name is Celtic; she was the personified spirit of a spring that welled up out of the ground to feed a pool. The identity of this water-spirit is known from the inscribed dedications to her which bear her name. Coventina was not exclusive to Britain: there is evidence that devotees worshiped the goddess in North-west Spain and at Narbonne in southern Gaul. Read more
Coventina was a Romano-British goddess of wells and springs. She is known from multiple inscriptions at one site in Northumberland county of the United Kingdom, an area surrounding a wellspring near Carrawburgh on Hadrian's Wall. Read more
The Lady of the Lake is usually referred to by various spellings of the names Nimue or Vivienne. Nimue is thought to be related to Mneme, the shortened form of Mnemosyne, one of the nine water-nymph Muses of Roman and Greek Mythology who gave weapons, not unlike Arthur's sword, to the heroic Perseus. Vivienne betrays the Lady's Celtic form, for "Vi-Vianna" probably derives from "Co-Vianna", a variant of the widespread Celtic water-goddess, Coventina. Source