Mark’s logbook also showed that the longest period of time he had gone without surfing since 1969 was three weeks. That happened in 1971, during a brief stint in college in Arizona. Since then, he had twice been forced out of the water for periods of slightly less than two weeks by injuries suffered at Ocean Beach. Otherwise, he had rarely gone more than a few days without surfing, and he had often surfed every day for weeks on end. Jessica Dunne, a painter, with whom Mark has lived since college, says that when he doesn’t surf for a few days he becomes odd. “He gets explosive, and he seems to shrink inside his clothes,” she says. “And when he hears the surf start to come back up he gets so excited that he can’t sleep. You can actually see the muscles in his chest and shoulders swelling as he sits on the couch listening to the surf build through the night.” In a sport open only to the absurdly dedicated—it takes years to master the rudiments of surfing, and constant practice to maintain even basic competence—Mark is the fanatics’ fanatic. His fanaticism carries him into realms that are literally uncharted, such as the Potato Patch. “One thing about Doc,” says Bob Wise, who has been surfing in San Francisco for almost thirty years. “He keeps open the idea that anything is possible.”

With me, Mark for years kept open the possibility that I might rise before dawn on a winter day, pull on a cold, damp wetsuit, and throw myself into the icy violence of big Ocean Beach. I came to dread his early-morning calls. Dreams full of giant gray surf and a morbid fear of drowning would climax with the scream of the phone in the dark. For most surfers, I think—for me, certainly—waves have a spooky duality. When you are absorbed in surfing them, they seem alive, each with a distinct, intricate personality and quickly changing moods, to which you must react in the most intuitive, almost intimate way—too many surfers have likened riding waves to making love—and yet waves are not alive, not sentient, and the lover you reach to embrace can turn murderous without warning. Somehow, this duality doesn’t seem to haunt Mark. His conscious life and his unconscious life have a weird seamlessness. His surfing dreams, as he recounts them, all seem to be about recognizable places on recognizable days. He notes the tides and swells in his dreams as if they were going into his logbook. If he’s upset when he wakes, it’s because he was looking forward to riding one more dream wave. His voice on the other end of the line at dawn was always bright, raucous, from the daylight world: “Well? How’s it look?”

Mark can see the south end of Ocean Beach from his apartment. I, during the years I lived in San Francisco, could see the north end from mine. I would stumble, shivering, to the window, peer through freezing, blurry binoculars at a cold, wild sea.

“It looks . . . scary.”

“Well? Let’s hit it!”

Other surfers also got these siren calls. Edwin Salem, a onetime protégé of Mark’s, says he used to be awake half the night worrying that the phone would ring, and then panic if it did: “Doc only called me when it was big and he knew nobody else would go out with him. I usually would.”

Everyone who surfs has a limit to the size of the waves he will venture among. The surfers in an area come, over time, to know one another’s limits. In San Francisco, this mutual knowledge creates a dense little community, nervous and drawling, in the beach parking lots on big winter days—men pacing back and forth, fists plunged in pockets, discussing the matter with dry mouths, laughing too loudly, while, out at sea, frightening waves rear and collapse. We study the waves, study the channels, trying to decide if the surf is within the range we can conceivably handle. That range is as much psychic as physical, and it is inseparable from the group: if X goes out, that doesn’t necessarily mean I have to go out, but if Y goes out, I’ll have to follow, because anything within his range is, I know, within mine.

When I lived in San Francisco, the only other surfer whose range approached Mark’s was Bill Bergerson, a local carpenter whom everyone called Peewee—an unlikely nickname, left over from the days when he was somebody’s younger brother. Peewee is a quiet, intense, exceptionally smooth surfer, probably the best pure surfer San Francisco has produced. His interest in big waves is not, however, indiscriminate. He does not try to surf every big day that comes along; he will ride big waves only when they are clean. Mark, for his part, will go out in borderline madness, when no one else will even consider it. Then he will go out in sheer madness. And come in laughing. Worst of all, he is not shy with other people’s demons: Edwin’s, his patients’, Wise’s, mine.

One of my demons was surfing itself. It had started out as a boyish passion, but it had long since turned into something else. I’d been surfing for nearly twenty years when I moved to San Francisco, in 1983, at the age of thirty. There had been periods when I didn’t surf—while I was living in Europe, or Montana, or New York City—but I had always found my way back to it. All in all, I had spent a staggering amount of time and energy looking for and riding waves. In the early nineteen-eighties, one of the surfing magazines (there are several) published a list of what its editors reckoned were the ten best surf spots in the world, and I realized I had surfed nine of them. What was more, the best wave I had surfed was not on the list. That was because only a handful of people knew that it existed. Finding that wave, off an uninhabited island in Fiji, had been the high point of a trek that kept me out of the United States for nearly four years. The search for new waves had carried me to strange and wonderful places—immersing me, once or twice, so deeply in the life of tropical fishing villages that, laid low by malaria, I nearly stayed for good. But it was an odd thing to arrange one’s life around. By the time I moved to San Francisco, I had been firmly confining surfing to the sidelines of my life for several years.

Mark undertook to reverse this trend. He had written to me in New York when he heard I was thinking of moving, sending a photograph of himself on a beautiful, wind-brushed Ocean Beach wave—a wave he claimed was merely “average”—and, once I got to town, he seemed to expect me to be ready to surf at all times. He knew I had another life, but he wouldn’t hear “excuses.” My ambivalence about the sport drove him nuts. It was heresy. Surfing was not a “sport.” It was a “path.” And the more you poured into it the more you got back from it—he himself was the exuberant proof of that. I knew I wasn’t the only object of Mark’s exhortations to take surfing more seriously, and my ambivalence persisted, but his enthusiasm had its effects. It got me out in the water more often than I would have gone otherwise; it also got my attention. Surfing and I had been married, so to speak, for most of my life, but it was one of those marriages in which little is said. I rarely talked about surfing, didn’t write about it, didn’t even think about it much. It contributed little to how I saw myself. I just did it—less constantly now than before, but no less automatically. Mark wanted to help me and surfing patch up our stubborn, silent marriage. I didn’t think I wanted it patched up. Having a sizable tract of unconsciousness near the center of my life suited me, somehow. And yet, over the course of my first winter at Ocean Beach, I found myself beginning to fill notebooks with surf-related sketches, oceanographic observations—and descriptions of Dr. Renneker.