it's known as the 'Blue Lagoon', but the flooded former quarry near Buxton hides a toxic secret.
It's so polluted that it's almost as toxic as bleach.
There are warning signs that state the water can cause skin and eye irritations and stomach problems, but people continue to swim there.
More top news
Misty again overnight. Murky and damp conditions returning to the Pennines. Grey start Friday but warm sunshine will develop from the west
Your weekend weather outlook for the Northwest and Isle of Man
Accrington have appointed John Coleman as the club's new manager for a second time.