Some say it’s the closest thing to space walking you will ever get. Silfra is a river in Iceland so clear that if it wasn’t for the bubbles, you would think you were floating in just air. The water is melted glacial water that has been filtered through the lava bed for years, and the temperature is always 2-4°C (just above freezing point). Because of the cold, there is no life in the water; therefore it is so clear, you can see over 100 meters.