Silfra

Silfra is a fissure in Thingvellir National Park in southwest Iceland, formed along the rift where the North American and Eurasian tectonic plates are pulling apart. It is fed by glacial water filtered through porous lava rock over decades, giving it exceptional clarity and a cold, steady temperature reported at around 2 to 4 degrees Celsius. The site is divided into sections, including the Silfra Cathedral and Silfra Hall, with depths reaching about 18 metres at the deepest basin. It is rated a technical dive, and the cold water is a significant factor, with divers and snorkelers wearing drysuits throughout. Marine life is minimal, limited mostly to bright green algae and small fish, since the draw here is the geology, the visibility, and the chance to drift between two continental plates rather than reef life.