THINGVELLIR, Iceland (AP) -- 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.
For snorkelers, traversing Silfra lasts 30 to 40 minutes; any more than that and the water temperature -- 2 C (36 F) -- makes one's face hurt. The "dry suits" that cover everything but face and hands provide enough flotation that even a weak swimmer can make the trip with confidence -- though there is one section where the current has to be fought a bit lest the snorkeler get swept into Thingvallavatn lake.
Kotze promised that anyone who ended up in the lake would be rescued, but it would take awhile -- a daunting prospect at these temperatures.
For those who steer clear of the lake, the coldest part of the trip will likely be topside. There are no changing rooms, so divers and snorkelers have to lever themselves into their suits in a wind-whipped parking area.
Waiting for others to complete their change of dress gives the chance to absorb Thingvellir as a whole. The valley is part of the near-obligatory Golden Circle route of natural wonders, which also include the thundering zigzag waterfall of Gullfoss and the Geysir thermal field where a geyser gratifyingly goes off every 5 to 10 minutes. Compared with those kinetic attractions, Thingvellir may seem underwhelming; it needs some contemplation to take it in.
Observing the mountains around the valley is like reading a taciturn tale of Iceland's creation; some pointed, some nearly flat-topped, one resembling a giant dirigible hangar. The motley forms suggest the chaotic, competing forces of the Earth's creation; although Iceland is some of the planet's newer land, it seems impossibly old.
Thingvellir is also of essential historical resonance for Icelanders. Viking clans chose the valley as the spot for an annual assembly beginning in the year 930, forming the world's first parliament. Almost no physical trace remains of those gatherings. Iceland quietly leaves it to the visitor's imagination to people the valley with merchants and charlatans and men declaiming from the Logberg, the "Law Rock." In a tourist-intensive age, it is an idiosyncratically modest choice, and more satisfying in the end than reconstructing Viking huts and paying actors to wear horned helmets.
In a way, a plunge into Silfra is way for a tourist to shed his life of ease for a couple of cold hours and fancy himself as tough and fearless as the figures in Njal's Saga, the tale of ancient Icelandic blood feuds.
Not that the Vikings went snorkeling. In fact, Kotze said, Silfra had a much less appealing use a millennium ago -- as a Viking toilet.
There were clashes at the annual assembly and because Silfra is narrow and depressed, the Vikings "went down there to do their business" with peace of mind.
If You Go...
SILFRA, ICELAND: Several outfitters including DIVE.IS -- http://www.dive.is -- offer snorkeling and diving trips to Silfra, about a 45-minute drive from Iceland's capital, Reykjavik. Prices for snorkeling are around 15,000 kronur ($120) and for diving about 35,000 ($273). The prices include transportation from Reykjavik, but divers who want to save a little money or spend a few extra hours exploring Thingvellir can get to the park on scheduled buses during summer. Dry suits and gear are included, but participants should bring thermal underwear and warm socks. Hot drinks and cookies are provided afterward, but the easily chilled may want to bring along a sandwich or other food to refuel their internal furnace. The trips can be expanded into full-day excursions that include time to explore Thingvellir and visit the renowned Gullfoss waterfall and Geysir thermal field.