I recently went swimming in one of these submerged mines/quarries in North America. This one flooded during a severe hurricane: https://en.wikipedia.org/wiki/Portland_Brownstone_Quarries

The Minnesota Iron Range is full of these and they're absolutely beautiful; terrifyingly deep, however.

[1] https://www.youtube.com/watch?v=LAL_d-5FsGQ - Tioga Pit Mine (225' deep)

[2] https://en.wikipedia.org/wiki/Portsmouth_Mine_Pit_Lake (450' deep)