From a geographical point of view, it’s a remarkable place. In 1789 several fissures were formed in the area as a result of earthquakes. The Silfra fissure cut into an underground spring filled with melting water from the Langjökull glacier. This water is filtered through porous underground lava - the filtering takes between 30-100 years - before arriving at Silfra, some 60 km away. It is therefore as pure and filtered as water can be.
Silfra is also remarkable because it is the only place on earth where you can swim between two continents and between two tectonic plates: The North American and the Eurasian plates. The Silfra fissure lies basically in a crack between the two. One of the distinctive things about Iceland – which sits on the Mid-Atlantic ridge - is that it has over 130 volcanoes.
But swimming, snorkelling or indeed scuba-diving in Silfra is not for the faint-hearted. Firstly, the water temperature averages at around 3° Celsius, so it’s absolutely freezing! Secondly, if you’re scared of heights, this might be magnified because the depth of the water is so clear to see.
The best way to keep warm is to wear a dry suit. This is a technical piece of kit that doesn’t allow any water to get in and since it keeps you completely dry, there’s the added bonus that you can wear thermal layers underneath.
Once you have tackled the cold, you can experience a spectacular site of unique volcanic geology, of vibrant shades of blue water, of stunning green ‘Trolls Hair’ algae, at a site that PADI rates among the top 10 in the world for diving.
Thingvellir National Park In Iceland | Adventures.com
Iceland's Silfra Fissure | Diving & Snorkeling | Arctic Adventures
Silfra Fissure: The Crack between the North American and Eurasian continents - Geography Realm