Loch Na Fideil was reputedly the home of a legendary female creature or spirit known as the Fideal after which the body of water is named (Loch of the Fideal). Depending upon which source you read, she attacks either men or women and children, dragging them down under the water in order to devour them.
Specific Location: Loch Maree
Until the middle of the 18th century bulls were sacrificed on August 25th (St Maerlrubha’s Day) to dragons that dwelt in the lake. These may have been akin to the creatures still reported in other Scottish Lochs to this day.
Taken from an article by Richard Freeman.