REYKJAVIK, Iceland -- I am sitting in a century-old, rock-lined pool dug directly into the tufted hillside behind me. Actually, behind us. I am not alone. I'm with Eeva Sutinen. We hardly know each other, but she was kind enough to bring me to this closely guarded secret, her bathing spot, hot springs deep in the rural southwestern corner of Iceland.
Neither of us has a watch and neither cares. Soaking under the cosmos, we talk for hours, up to our chests in bath-warm water, a C-shaped wedge of moon spilling like a teacup above us. We are completely, and platonically, naked, though we met only the day before.
Later, we make our way back to her home, near greenhouses glowing like amber-lighted jewels. By now, it must be midnight. She shows me the living room couch and says goodnight. When I awaken, I find a note saying to help myself to what's in the fridge. Eeva, originally from Finland, has already left for work in the greenhouses. It's entirely possible I will never see her again.
On my own, never in a hundred years of wandering Iceland would I have found Eeva or her hot springs. Thanks to online travelers' communities like the Couch Surfing Project, however, strangers meet, put each other up for the night, and possibly enjoy extraordinary if ephemeral encounters.
My ''couch surfing" began for practical reasons. In April, I was planning a six-day stopover in Iceland on a budget so tight I could have lost my money belt between the pages of my Rough Guide. The youth hostel in Reykjavik was booked solid. To avoid a pricey hotel room, I decided to try free accommodation through a hospitality exchange club like Couchsurfing.com.
Here's how it works: Anyone can create a free online profile that describes themselves, where they live, and whether they have a couch to offer other surfers. Travelers can search for hosts in the places they want to visit. E-mails are exchanged and plans are made, as long as both parties -- host and surfer -- are comfortable with the arrangement.
''Ultimately, couch surfing is becoming a brokerage for adventure," says Couchsurfing.com founder Casey Fenton, from Conway, N.H., where Couchsurfing is based. ''We're not just a place to stay for the night. We're here to create memories, have cultural exchanges, perhaps make friends and stories to tell your grandkids."
Fenton, a computer programmer, says the idea for his website began percolating in 1999, when he was traveling to Iceland. Looking for a couch to crash on, he spammed some 1,500 Icelandic students in Reykjavik. Favorable responses led to what he called ''an amazing, crazy weekend." On the plane back to Boston, he said he thought, ''That's how I want to travel . . . every time."
Teaming up with Daniel Hoffer, a Brookline native and Harvard University grad, and two others, Fenton launched his not-for-profit service last year.
This kind of informal cultural exchange goes back to SERVAS, an organization founded in 1949. But with massive online databases -- Couchsurfing has 13,686 surfers from 135 countries at last count -- these modern-day organizations truly harness the power of the Internet's connectivity.
''The more people are doing this, the more legitimacy is lent to the whole idea," Fenton says.
Since I signed up on Couchsurfing.com, I've had inquiries from Canadians, an Austrian, a college student from California, and a Florida woman. My first couch surfers -- two guys on motorcycles from Montreal -- were supposed to arrive one weekend last month but their plans changed. Since then, I've been away too often to be a host, but I eagerly await my first guest. The woman from Jacksonville contacted me about crashing at my place when she passes through Boston this fall.
Staying with strangers opens all kinds of doors. I didn't meet Eeva through couch surfing, but rather by way of her friend, Hanna Arima, whom I had contacted through another online network called Globalfreeloaders.com. Hanna, also Finnish, trains horses and studies saddle making on a farm near Hella. I spent one night with her and Eeva, who was visiting Hanna in her basic accommodations above the stables. I was Hanna's first surfer, and because I turned out OK, Eeva invited me to stay the second night with her.
While we were sightseeing through the region's pasturelands, I asked them if they were concerned about an American they didn't know spending the night.
''Usually, I just trust that people respect me," Hanna said. ''I was getting e-mails from someone, but I sensed it was not right. So I just told him he could not stay with me."
Security isn't foolproof, Fenton says, but on Couchsurfing.com, each traveler or host can be vouched for by fellow couch surfers. ''We can't guarantee the trustworthiness of everyone. All we can do is provide the info and connections. People need to use their street smarts."
While free lodging is an obvious benefit, I soon realized that staying with locals would significantly alter my Iceland experience. My first hosts, a young couple named Thrainn Gislason and Thurithur Anna Robertsdottir Darling, cooked me a hearty meal of Icelandic lamb and took me out on a nearby rooftop terrace for a sunset view over Reykjavik.
My second host, Sveinbjörn Sveinbjörnsson, had returned from two weeks bumming around Thailand and Cambodia only the night before I arrived. He is a true adventurer; his online profile lists hang gliding and mountain sports as his hobbies, and his family owns all manner of off-road vehicles. He told me he had hosted two women from San Francisco in January and took them four-wheeling on a glacier.
''When I found out about this couch surfing, I signed right up," Sveinbjörn said over a meal of burritos he had cooked for me. ''This is the thing for me."
We hit it off immediately. Besides feeding me and putting me up, the gregarious Sveinbjörn and his girlfriend, Ásta Ósk Stefánsdóttir, introduced me to a half dozen of their friends, took me out to bars and nightclubs till 4 a.m., and bought me far too many drinks. The day I left for the airport, Sveinbjörn told me, ''I wish I could have done more."
How do you repay such generosity? Actual compensation would be an insult. I had just come from Paris, so as a gesture, I brought my three Icelandic hosts bottles of Bordeaux and a wheel of shrink-wrapped Camembert. I cooked dinner for Sveinbjörn and Ásta; with Eeva and Hanna, pizza was my treat. I promised to see them again, and hoped they would stay me with someday.
Guests are expected to host a surfer, but not necessarily the person who hosted them. In an age of mistrust and terror, the whole movement is intended to be an international network of good will.
My last day in Iceland, I realized I had left my camera case at Eeva's. She had it sent down to Reykjavik, and included a lovely note about our time together.
''I have an enormous debt to this mankind," she wrote, describing years of hitchhiking and relying on the kindness of strangers. ''I was just passing my hitchhiking debt over to you. I got the feeling that you are going to pass it forward."
And I will.
As for the hot springs' location, Eeva swore me to secrecy. But if you ever connect with her in Iceland, she just might take you there herself.
Contact Ethan Gilsdorf, a freelance writer in Somerville, at email@example.com.