BOOK REVIEW / NONFICTION : An Ecological Guilt Trip by Kayak Through the Sea of Cortes : KAYAKING THE VERMILION SEA: Eight Hundred Miles Down the Baja <i> by Jonathan Waterman</i> , Simon & Schuster, $22, 256 pages

Alan Watts once observed that some spiritual seekers are so profoundly ill at ease with the frailties and foibles of human existence that they secretly prefer the vision of Earth as a bare rock scrubbed clean of humanity.

The same is true of a certain breed of adventurer and eco-activist, as we begin to suspect in Jonathan Waterman’s “Kayaking the Vermilion Sea,” an account of his voyage by kayak through the Sea of Cortes, “this desert Polynesia.”

“The orange orb of sun . . . illuminates everything as it has since the beginning of time, before humans,” Waterman writes of a Baja sunrise. “My awe for the cleanness of each morning’s sunrise is rooted in privilege: We are witnessing one of the few age-old, natural events unaffected by technology or meddling mankind.”

Ostensibly, Waterman’s book is an armchair adventure about a kayaking expedition undertaken by the author and his wife, Deborah. But the real theme of “Kayaking the Vermilion Sea” is a man, a marriage and humankind itself in crisis.

Jonathan and Deborah Waterman are mountain dwellers (and mountain climbers) by nature, but they have descended from their Rocky Mountain aerie in search of an “adventure journey” which, they hope, will reinvigorate their lives and, as Waterman shows, jump-start their troubled marriage.

Waterman, for example, tells us that each of their kayaks is loaded with “190 pounds of food, fuel, water and gear” (he acknowledges the corporate donors who provided most of the stuff) but it is their emotional baggage that really burdens the author.

“Out among the simplicity of sea and sky I hope to find a way to release this notion that our days are all too short and fragile,” he allows, “this gut feeling that, in the end, life may be worth nothing.”

As if an early onset midlife crisis were not enough to make him miserable, Waterman is also the victim of an all-pervasive environmental guilt trip that informs virtually every aspect of his daily life. Thus, when Deborah is writhing in pain from a migraine attack, Waterman confesses, “I indulge my theory about how the sea has been violated and maybe we’re taking on its pain.”

Indeed, as Waterman surveys the despoliation of Baja California and the Sea of Cortes, he weighs all of humanity and finds it wanting. For example, when the author nearly steps on a rattler outside his tent, his first impulse is to kill it. Deborah stops him short with a guilt-inducing gasp, and so he merely chases the snake away with a paddle. But he spends the rest of the night in angst because the snake incident somehow reminds him of the damming of the Colorado River back in 1935.

“The knowledge that technology has prevented a vast river from clashing with the sea, the knowledge that I am not separate from the dam, makes me toss and turn for hours,” he writes. “I wonder if it is innately human to try and dominate the natural world--for in my desire to kill the snake, am I the same as those who killed the river?”

Waterman’s frustration at teeming humanity is not restricted to dam builders; he is also bugged by sport fishermen, American expatriates, novice hikers, native entrepreneurs, and so on. But he is considerably kinder when he contemplates dolphins, needlefish, roaches--and himself.

“I am not yet gray,” he sings of himself, “and I am one of those lucky people who does not mind hard work and who occasionally laughs and plays like a child.”

“Kayaking the Vermilion Sea” offers more than a few moments of pleasure and revelation. Waterman conjures up the enchantment of his encounter with the sea in (mostly) unspoiled waters; he introduces us to the exotic (if endangered) wildlife of the Sea of Cortes; he allows us to glimpse what it is like to match oneself against the blind (but benign) forces of nature; and, now and then, he harks back to the history of Baja California, if only to make the point that men have always treated the land, the sea and each other rather abominably.

So I suppose that we should not carp about Waterman’s role as a kind of self-designated ecological Cassandra; after all, Cassandra may have been a Gloomy Gus, but she turned out to be right. Still, “Kayaking the Vermilion Sea” reminds us that the messenger is sometimes even harder to take than the bad news that he bears.