The air above the Silfra rift was freezing and the water in it was only a couple degrees higher, just warm enough to be liquid. Going under was a small shock to the skin — but stunning to the eyes.
The weak light of a grayish Icelandic winter day transformed into an intense glow of blues and greens, offset by brown and golden sand and rocks. From above, Silfra is just a dull ditch between dark chunks of lava; from below, an extravagant, eerie maze.
If the sights don’t take up all available brain cells, a snorkeler or diver can also wonder at how he is, with a bit of poetic license, swimming between two continents.
Silfra lies in Thingvellir, a broad valley about a 45-minute drive from the capital Reykjavik that was formed as the European and North American continental plates slowly pull apart. The rift is filled with water that seeps through lava from the Langjokull glacier some 50 kilometers (30 miles) away, a decades-long process that filters the water to absolute purity and allows subsurface visibility of 100 meters (350 feet).
The startling clarity, and presumably the bragging rights of braving subarctic waters, have made Silfra an incongruously popular spot for a sport usually associated with tropical lushness. Its global appeal was quietly underlined when Louis Kotze, the guide on a recent trip, mentioned that he was a native of Namibia.
Divers who relish the teeming life and riotous palette of coral reefs occasionally complain that Silfra, with few fish and little vegetation, is dull. But Silfra is better seen as a primeval precursor of Scandinavia’s design sense — austere yet soothing — and as a peek into the geological drama of the island’s formation.
There are shallow sections where swimmers skim above rippled tan sand within arm’s reach. Elsewhere sheer lava walls plunge down 20 meters (65 feet) or more; the snorkeler can only envy divers who have the gear and skills to sink through the gradations of turquoise and sapphire light.