I found this about an old scottish loch creature .Hector Boece's work published in 1536 The History and Chronicles of Scotland, was mainly stories collected from people he spoke to. Duncan Campbell, told him a story about a loch monster. In 1510, a beast rose from the waters of a loch called Garloll in Argyll-shire, Scotland. Campbell described it as being as big as a large dog like a wolfhound but it had the feet of a gander. It was so large it could knock down trees with it's tail and it killed three hunters by hitting them with it's tail. It then fled back to the loch. It was said to be a bad omen if the beast rose .There isn't a Garloll in Scotland but there is Loch Gairloch in Wester Ross, in the North-West Highlands of Scotland.
(you can find the original version on google books to read)
There is also a malevolent seahorse called the Tangie said to inhabit Britain's Shetland and Orkney Islands. It resembles a scruffy pony with a long shaggy mane of seaweed. It likes to frighten travellers along the lochs at night and devours young women.
Further north is the Havhest or sea-horse. It is a Sea-Serpent in Scandinavian folklore. It has a horse like head and the tail of a fish.It has many characteristics such as glittering yellow eyes, a long mane down its back, and forelimbs like a seal’s,plus a double row of fangs and it can breathe fire,It is blamed for sinking ships and has only been seen a few times since the nineteenth century.
A round up of a few beasties you may not have heard of.Some of the old stories have similar traits and the descriptions are often horse like which reminds me of the water horse legends. They were all said to live in lakes and lochs. Folklore passed down through the generations...or some truth in it? You decide .