The Dobhar-chú, an Irish folktale

Nestling in the Glenade Valley (from the Irish “Glen of Jealousy”), Glenade Lake sits amid spectacular scenery, within sight of the towering peaks of the Dartry range of mountains.

According to popular folklore, the waters of the lake, located in the northwest of Ireland, are home to a species of monstrous otters known as the Dobhar-chú. Their name literally translates to ‘water-hound’, and it was not by chance an old Irish term for otters.
In one version of the story it is said that when a regular non-magical otter has seven children, its seventh cub will become a Dobhar-chú.
Although usually described as resembling a common otter in appearance, there is at least one variant of the story in which the Dobhar-chú had a sharp horn protruding from its forehead.
Another important characteristic is that their bodies were protected by a potent enchantment that rendered the creatures immune against attacks from any weapon. There was only one unprotected weak point, which was a small spot located under the breast of the animals. Thus, the only way to kill a Dobhar-chú is by attacking that spot.

In modern interpretations, the creature is most commonly depicted as either a regular otter or an otter with some monstrous characteristics.
The area surrounding Glanade Lake has also a local myth about these creatures.
The details were well known one time and the ballad sung at fairs on the streets of Kinlough. Some say a woman went to the lake to wash clothes, but the ballad tells she went to bathe.
As the story goes, the woman named Grainne lived by the lakeside. One day, supposedly around 1722, she went to wash her clothes in the water, but unknowingly encroached upon the territory of a Dobhar-chú while doing so.
The creature killed the intruder without mercy.
Seeing that his wife hadn’t returned home, her husband, a brave fellow who went by the name of Traolach McLoghin, set out towards the lake and saw the otter-like creature resting on top of his wife’s corpse.
Magical creature or not, this was horrible, and the man went back home to fetch his dagger.
When he returned, the Dobhar-chú was still sleeping and he swiftly stabbed it in its weak spot.
With its dying breath, the creature let out a loud whistling noise.
The man did not know what to make of this, but the elders of the village knew the ways of the fae, for they were wise and experienced, and they told him that the creature had called upon the others, and advised the man to flee with great haste.
Thus, the man gathered his horse and left the village together with a close friend. As the two men were fleeing, they noticed that a second otter was pursuing their horses with incredible speed. Try as they might, the men failed to lose their pursuer.
With no other choice, the men halted their horses and stopped near a cluster of ruined walls. The creature ran between the legs of one of the horses and attempted to attack the men, but it was stabbed in its week spot and killed.
In the version where the creature had a horn on its head, it impaled one of the horses before going down.

Interestingly the area, at the nearby ancient graveyard, Conwell Cemetery, has a gravestone-like monument that depicts the creature, and local tradition has it that this is the final resting place of the woman who was murdered by the monstrous otter, though the name of the woman, and the details of the story, often differ between versions of the tale.
Either way in the area, people would refer to her by the name ‘Grainne’ when telling the story, and the tombstone itself mentions the name ‘Grace’.

A similar story was told in Sracleighreen, also in Ireland.
Here too, a woman was said to be killed by a Dobhar-chú while washing clothes in a lake.
But there, in County Leitrim, the term Dobhar-chú refers to a hag or witch who rules over aquatic animals.

Images from web – Google Research