The each uisce is an Irish Water Horse.
Irish Gaelic "each uisce"
In all manifestations the each uisce is a fearsome creature who can deceive and torment mortals. A sleek and handsome steed, it almost offers itself to be ridden. When humans bridle and saddle them, they make fine horses, as long as they do not catch sight of salt water. When this happens, the each uisce bounds into the water with its helpless rider on its back; the horse may later devour the rider. Only the human liver will be rejected, which then floats to the surface.
An untamed each uisce might also devour mortal cattle. According to popular legend, St Féchíne of Fore (d. 665?) compelled an each uisce to pull his chariot when his own horse had died.
It belongs to the same family of water horses as the Scottish each uisge and the aughisky and bears some relationship with the Welsh ceffyl dwfr. It should not be confused with the beautiful, lake-dwelling horses Cúchulainn captured and trained; he returned those to their mountain pool of his own volition when they were mortally wounded. The shoopiltee is a variant of the each uisce from the Shetlands.
The water-horse inhabits salt water or large still bodies of inland water, and is thus distinguished from the kelpie inhabiting running water. The Irish each uisce is most likely to emerge from the water during the month of November (Samain), when it gallops along the sands or over fields.