The dobhar-chu (dobhar-chú, dobarcu, dobhar-choin, doyarchu, water hound, master otter) is an old Irish cryptid that resembled either, a sort of otter, a dog/fish hybrid or a serpentine creature. Though in all transformations it is commonly described with fur with protective properties such as an otter. In terms of colour it can range from white to brown or black.

The dobhar-chu is said to reside in lakes but with the capability of walking on land quite fast (In one tale it was said to keep up with horses). One legend attributes to its birth the 'seventh cub of the common otter' (Seán ó h-Eochaidh, n.d cited in Dave Walsh, 1998). It was known not to hesitate to attack humans for food.

There are at least two well known grave sites with the tale of the dobhar-chu associated with them. The first is the Kinlough stone said to mark the burial site of a woman killed by the dobhar-chu, even providing an image of the creature. The second is the Glenade Stone where a woman had been killed by the beast in similar circumstances in 1722 by lake Glenade. There is also a drawing of the beast there.

Some sources give us instances when the beast has attacked (Roderick O'Flaherty, 1684 cited in Dave Walsh, 1998). But by far the most well known tale, as taken from Patrick Tohall (1948, pp.127-129 cited in Dave Walsh, 1998) is the following:

'A woman named Grainne, wife of a man of the McLoghlins, who lived with her husband in the townland of Creevelea at the north-west corner of Glenade Lake, took some clothes down to the lakeshore to wash them. As she did not return her husband went to look for her and found her bloody body by the lakeside with the Dobhar-chú asleep on her breast. Returning to the house for his dagger he stole silently on the Dobhar-chú and drove the knife into its breast. Before it died, however, it whistled to call its fellow; and the old people of the place, who knew the ways of the animals, warned McLoghlin to fly for his life. He took to horse, another mounted man accompanying him. The second Dobhar-chú came swimming from the lake and pursued the pair. Realising that they could not shake it off they stopped near some old walls and drew their horses across a door ope. The Dobhar-chú rushed under the horses' legs to attack the men, but as it emerged from beneath them one of the men stabbed and killed it'

Though in some versions of the tale the latter beast had a horn with which it ran the horses through with. It should be noted that the modern Irish word for 'otter' is indeed 'dobharchú'.