Berkeley Pitt
Berkeley Pitt in Butte, Montana, is named for the enlightenment philosopher of the same name. Once a copper mine, the lake is now considered to be quite toxic due to the unsafe chemical composition of the water itself. Luckily, Montana is full of other swim-friendly locations you can try instead.
Beqa Lagoon
Beqa Lagoon, located in Fiji, is quite beautiful, as is its surrounding lush forests. However, this Lagoon is home to many sharks that can quickly surround an unsuspecting swimmer. Definitely keep this fact in mind when you’re looking to visiting this lagoon.