A Brisk Morning Scuba Dive Between Tectonic Plates

When the air temperature is 33°F and the water temperature is 35°F, you may as well go swimming.

In a small parking lot inside Thingvellir National Park in Iceland, Lisa and I awkwardly squirmed into our drysuits inside our rental car. Standing outside in the freezing wind to put the suits on was simply not an option. It was a little before 10am and we were about to do our first drysuit dive in the Silfra fissure.

Silfra is one of the most unique dive locations in the world, offering unparalleled visibility along with the rare opportunity to swim between the North American and Eurasian continental plates. There is a lengthy and fascinating geological history to the Thingvellir area: millions of years of magma plumes and earthquakes and eruptions and shifting tectonics. The result is a dramatic gash in the earth, which is one of the few spots on the planet where the division between the continental plates can be seen above ground.

And at some point roughly 12,000 years ago, near the end of the last Ice Age, the Langjokull glacier was retreating when a volcanic eruption buried the glacial melt water. Since then, the melt water has been slowly filtering back up through 50km of lava rock. It’s a 30- to 100-year journey that purifies the water far beyond what your Brita pitcher is capable of.

They say you can pull your regulator out of your mouth and take a drink. So after dragging our tanks across the parking lot, tossing on our fins, and carefully climbing down the steep metal staircase that leads into the fissure, that was the first thing I did. The geologists aren’t kidding: it’s the freshest, cleanest water you could ever hope to taste, chilled to perfection.

We descended below the surface and finally laid our eyes on the dramatic rock walls that make Silfra such a sought-after dive. Our guide swam ahead and snapped pictures of us with our hands firmly placed on two separate continents.

The stinging cold of the water was tough to get used to, but the reward was the Silfra Cathedral, the deepest point in the fissure, framed by 20 meters of jagged rock on either side, with enormous boulders coating the floor. As the continents shift a centimeter or two apart each year, the tension in the fissure builds, and earthquakes ultimately dislodge chunks of the wall. All that geological history was lying ominously below us.After the Cathedral, we entered the Silfra Lagoon, which shrinks in depth to only two or three meters. Our inexperience with our drysuits had us even bobbing up to the surface at points as we crossed the narrowest passage. The sandy bottom accentuates the acuteness of the visibility and a strange cotton-candy-like algae grows near the surface of the water, adding to the already-dreamy atmosphere.

The Lagoon marks the end of the dive, which is shorter than most. It’s really only a 400- or 500-meter swim from the entrance point to the exit point. The time flies by when you’re underwater…but when you realize that you now have to carry your tanks 500 meters back from the exit platform to the parking lot in the bitter winter wind, time manages to slow right back down again.

When people visit Iceland—especially off season—so much energy is expended in trying to keep warm. It is thus unthinkable to most that one would opt to dive into a crack in the ground full of near-freezing water. But living your life without experiencing the glory of Silfra: that is what should truly be unthinkable.