Great Lake

The Black Lake is a large body of water located to the south of the castle. It is about half a mile in diameter and the Hogwarts plumbing network drains into it.

History
Every school year at Hogwarts, first years sail across the lake to the castle led by Rubeus Hagrid in boats as per Hogwarts tradition. When they got to the school, they are then Sorted into their houses.

Triwizard Tournament


Students from Durmstrang Institute arrived at Hogwarts on their enchanted boat via Black Lake. As part of the Second Task of the Triwizard Tournament, the four champions Harry Potter, Fleur Delacour, and Cedric Diggory, and Viktor Krum had to swim in the lake for one hour to rescue something that was taken from them. Harry used Gillyweed to hold his breath for that long, while Cedric and Fleur used the Bubble-Head Charm, and Krum partially Transfigured himself into a Shark.

Dumbledore's Funeral
In 1997, Albus Dumbledore was laid to rest in a white tomb on the shores of the lake following his death in the Battle of the Astronomy Tower.

Inhabitants
It is home to a Giant Squid, grindylows, and a colony of Merpeople. The lake was also used as the site of the Second Task of the Triwizard Tournament. The Slytherin common room is beneath the lake, accessed through an entrance in the school dungeons. The Chamber of Secrets is also thought to be beneath the lake. At some point, Neville Longbottom's pet toad, Trevor, escaped into the lake, joining other toads that lived there.

Temperature
The lake is very often cold, but Viktor Krum is known to have swam in it, apparently not affected by the low temperature (although this is probably due to the fact that his school, Durmstrang, is located in a place that is even colder).

Lily Evans and her friends were also said to dangle their legs over the water, which could mean that there were no rules whilst they were in school against swimming in the lake.

Behind the scenes

 * In the films, the lake is known as "The Black Lake."
 * In Lego Harry Potter: Years 1-4, the lake has quays.
 * In the films Dumbledore's body is placed on a small island in the middle of the Black Lake. After this, in 1998, Voldemort accesses his grave and takes the Elder Wand from Dumbledore's grave.

Appearances

 * Harry Potter and the Philosopher's Stone
 * Harry Potter and the Philosopher's Stone (film)
 * Harry Potter and the Philosopher's Stone (video game)
 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * Harry Potter and the Chamber of Secrets (video game)
 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (film)
 * Harry Potter and the Prisoner of Azkaban (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Goblet of Fire (video game)
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Half-Blood Prince (video game)
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 1
 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)
 * Harry Potter: Quidditch World Cup
 * Lego Harry Potter: Years 1-4
 * Pottermore

Notes and references
Lac de Poudlard