There are a few places at Hogwarts we might think twice about visiting, and the Great Lake in the grounds is certainly one of them. But it isn’t the cold or the dark water we’re wary of, it’s what lurks in its depths…


Newt Scamander writing on Grindylows in his book, Fantastic Beasts and Where to Find Them: ‘A horned, pale-green water demon, the Grindylow is found in lakes throughout Britain and Ireland. It feeds on small fish and is aggressive towards wizards and Muggles alike, though merpeople have been known to domesticate it. The Grindylow has very long fingers, which, though they exert a powerful grip, are easy to break.'

Harry first came across a Grindylow in Professor Lupin’s office in his third year at Hogwarts. It wasn’t particularly friendly – ‘pulling faces and flexing its long, spindly fingers’ as well as ‘brandishing a fist at him’ from its tank. We found out that these water demons inhabited the Great Lake during the second task of the Triwizard Tournament. One grabbed Harry’s leg, although he was able to fend it off with an underwater Relashio spell and he spotted another as a merperson’s pet. However, it was Fleur Delacour who came off the worst, attacked by the Grindylows and unable to retrieve her little sister from the lake.


Newt Scamander writing on merpeople in his book, Fantastic Beasts and Where to Find Them: ‘Merpeople exist throughout the world, though they vary on appearance almost as much as humans […] The oldest recorded merpeople were known as sirens (Greece) and it is in warmer waters that we find the beautiful mermaids so frequently depicted in Muggle literature and painting. The selkies of Scotland and the merrows of Ireland are less beautiful, but they share that love of music which is common to all merpeople’.

The merpeople in the Great Lake played a vital part in the second task of the Triwizard Tournament. It was their song that formed the clue inside the golden egg, and they were tasked with guarding the friends, family or lovers that were taken from the four champions. In the Great Lake, the merpeople had ‘greyish skins and long, wild, dark green hair. Their eyes were yellow, as were their broken teeth’ and, more alarmingly for Harry, many of them were carrying spears. We certainly wouldn’t want to cross them, as Harry found out when he tried to take more than one hostage…

Giant squid

Writing on about the giant squid that lives in the Great Lake, J.K. Rowling says it is ‘semi-domesticated and permits students to tickle its tentacles on sunny days, when it basks in the shallows.’

So although a giant squid sounds quite scary, it’s hard to be truly fearful of a creature that allowed the Weasley twins and Lee Jordan to tickle its tentacles. In fact, the giant squid seems like a pretty relaxed kind of creature to be around when we compare it to the other inhabitants of the Great Lake. Across the Harry Potter books, it was often seen propelling itself ‘dreamily across the surface of the lake’ or ‘waving its tentacles lazily above the water’. What a life, eh?

That being said, we’re still not sure we’d want to risk a swim.

Moaning Myrtle

J.K. Rowling writing on about ghosts: ‘In the world of Harry Potter, a ghost is the transparent, three-dimensional imprint of a deceased witch or wizard, which continues to exist in the mortal world…Should part or all of a ghost pass through a living creature, the latter will experience a freezing sensation as though they have been plunged into ice-cold water.’

Moaning Myrtle might be a ghost, but she told Harry that she – sometimes willingly, sometimes unwillingly – visited the Great Lake’s depths:

‘I sometimes go down there… sometimes don’t have any choice, if someone flushes my toilet when I’m not expecting it...”

Harry Potter and the Goblet of Fire

Myrtle might not have always been a cauldron full of laughs, but we have to say she really helped Harry out with the second task of the Triwizard Tournament. She gave him a clue that the egg should be held underwater whilst he bathed in the Prefects’ bathroom, and then – from her trips to the Great Lake – confirmed to Harry that merpeople did indeed live there. Although, like Harry, we’d rather avoid thinking ‘about Moaning Myrtle zooming down a pipe to the lake with the contents of a toilet’.

It definitely puts us off diving into the Great lake even more!