Located in the Þingvallavatn Lake in the Þingvellir National Park in Iceland, Silfra is a rift that is part of the divergent tectonic boundary between the North American and Eurasian plates.
For divers, the glacial water is very cold at 2-3 degrees C, but the payoff is very clear vis - similar to some of Mount Gambier's sinkholes on a good day.
The water in Silfra is pure, filtered and great to drink - Mt Gambier's sinkhole water is generally alkaline, coming through limestone - Silfra's water is filtered through volcanic basalt (and other rock).
Silfra is ice-free all year but the surrounding countryside is covered in snow during the winter. We dived with Dive.is .