Tiger Lake

Lake Þingvellir is formed where a depression and cracks in the ground from the rift between two tectonic plates reveal underground water. On the northern part of the lake fresh filtered water flows from underground into the lake. This underground water is exceptionally clear. Diving in popular in the underground fissures and ravines where visibility can be over 100 meters. This underground has a very consistent temperature during the year and where it flows to the surface, patches of unfrozen water can be seen. 
Photo © copyright by Örvar Þorgeirsson.