The Blue Lagoon near Buxton, a flooded quarry - has inviting turquoise waters, but it is so polluted it's almost as toxic as bleach.
There are warning signs saying it can cause skin and eye irritations and stomach problems, but families and young swimmers are ignoring them.
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Another wet day tomorrow with rain continuing throughout the morning.
Heavy rain gradually moves away northwards, however it will remain cloudy with further periods of rain.
Nottingham Trent University has released a statement after building cladding inspections led to the temporary relocation of some students.