Cìrein Cròin: Scottish Sea Monster
Cìrein Cròin was described as a colossal sea monster and was known by many names or alternatives spellings. Some of those other names are:
mial mhòr a’ chuain (the great beast of the ocean)
curtag mhòr a’ chuain (the great whirlpool of the ocean)
uile bhéisd a’ chuain (the monster of the ocean)
ceirean
Cirein-croin
Cionarain-cro
"A sea monster in Scottish Gaelic folklore, thought to be the largest of all living creatures, capable of making a meal of seven whales." A Dictionary of Celtic Mythology by James MacKillop (2004)
The great sea beast represented the uncontrollable nature of the sea, making it something to be both respected and feared.
This was the largest animal in the world, as may be inferred from a popular Caithness rhyme: ‘Seven herring are a salmon’s fill, Seven salmon are a seal’s fill. Seven seals are a whale’s fill, And seven whales the fill of a Cirein Croin.’ A Encyclopedia of Fairies by Katharine Briggs (1976)
Cìrein Cròin is sometimes described as a sea serpent, but other times is simply called a sea monster or sea beast.
Many people online state that there is a story where Cìrein Cròin can transform into a small silver fish. Once he is caught up by fishermen, he transforms back into his true form and eats the humans.
Sadly, none of the pages online seem to say where this story is sourced from, and I haven’t found it’s origin myself just yet.