What’s it like to snorkel between two tectonic plates in glacial waters? David Whitley squeezes into a dry suit—and explores a whole new (in-between) world.

At the water’s edge, the humiliation of being helped into a dry suit for what seems like hours suddenly feels like a worthwhile trade-off.

This is no ordinary snorkeling experience of flitting fish and swaying coral in warm, tropical seas. It is a plunge into the gap between two continents—a gap that happens to be awkwardly close to the Arctic Circle.

This is the Silfra fissure. Formed by the Eurasian and North American tectonic plates slowly ripping apart, it cuts through the Þingvellir World Heritage Site, a spectacularly bleak expanse of tuftily-mossed lava fields with stark mountains jutting up on the horizon and bone-rattling North Atlantic winds gusting through. It’s where Iceland’s first parliament—and the world’s oldest—first met in the 10th century; the national flag flies proudly beneath the intimidating rock wall.