In 1719, British forces burned many homesteads along the loch's shores in the month preceding the Battle of Glen Shiel.
A legend connected with Loch Duich states that three brothers who went fishing at the loch one night became enraptured by three seal-maidens who had thrown off their furs, assumed the likeness of humans, and danced in the moonlight on the sands.
For his kindness, the girl's father allowed the youngest brother to visit the maiden every ninth night.
It is still a mystery as to whether the films exist at all, but are accepted by several Loch Ness researchers.
The designation is in place to protect the lochs' burrowed mud and their flame shell beds.