AIR hisses out the shoulder valve of the buoyancy compensator. Again, I tenderly tug on the release hose. More air escapes. I'm barely afloat now; only the top half of my neoprene-encased head bobs above the cold swells. The surface of the ocean bisects my vision through the glass mask. Above, I see a familiar blue sky alive with sea gulls. Below, an aquamarine soup and the obscured outlines of fish and algae. Steve, my private instructor who's an ex-Green Beret, points thumbs-down: Time to descend."Ninety percent of this sport is mental," he has told me. "You must think of what you're doing." We exhale and gradually begin to sink. I think of the bowling ball he tossed into the training pool as an example of the physics I must master. It sank, but then slowed and hovered at eight feet. Natural forces in balance - gravity pulling the black sphere toward the earth's core, the dense water underneath pushing it heavenward. Slung around my hips, 28 pounds of lead offsets the buoyancy of the full-body wet suit, vest, and air tank. Unlike the bowling ball, I must actively control my near-weightlessness. Every couple of feet, I pause to pinch my nose and blow. My eardrums pop, equalizing the pressure imbalance that mounts in my head. With depth, the ocean compresses the wet suit. I must spurt a little air into the vest to compensate for this effect and maintain a slow descent. It seems there's so much to remember today - my fi rst day of open-water diving. Steve flashes me an OK sign at bottom. My gauge reads 33 feet. Surrounding me is a world I've always hoped to visit. A glade of kelp grows upward from the life-encrusted granite slabs. Scattered about with the regularity of redwoods in a terrestrial habitat, tangled ropes of giant kelp (Macrocystis pyrifera) span the distance from sea floor to surface. Attached to the clumps of ropes, droplet-shaped floats with scimitar blades of golden-green keep each plant vertical and allow the elastic stems to sway gently with the ocean's heartbeat. This is a forest I have entered in reverse. Floating down from its upper canopy, through its understory to the floor. It strikes me as a topsy-turvy woodland where the trees are not supported by their trunks, but rather held up by their leaves. I can see, at most, 10 feet ahead. The saltwater first captures the warmer, longer wavelengths of radiation. Dusky blues and greens are what remains. Shreds of kelp, millions of suspended phytoplankton and one-celled larvae, also add a haze to the water. Late summer winds have reshuffled the California current offshore. As a result, the murky broth from the submarine canyon has funneled into this kelp forest of Monterey Bay. After a week and a half of thorough pool training and lectures on the dangers and pleasures of scuba, the anticipation and tension of this moment at last releases itself. I have always wanted to be here - within reach of the bulldog-faced rockfish suspended in front of me and the translucent moon-like jellyfish that pulses over my head. The yearning to scuba dive first hit me in elementary school, when Mom and Dad carted my little brother and me to the Moss Beach tidepools, 10 miles south of San Francisco. I cheerfully collected dancing hermit crabs and small speckled eels in a mayonnaise jar. These wonders I'd show to anyone who'd look at them. Living in a cluttered beach bungalow in San Diego, I almost graduated from college in marine biology until journalism turned my head. A seven-year succession of demanding editing jobs left me no time to think of much outside of my work, let alone to ponder the ocean, until my mother became ill. My boss at the newspaper - a compassionate man - gave me a four-month leave of absence so I could help my family care for her at home. After Mom died, he understood when I asked for this extra month to explore my new world. Mom and I talked and wept a lot those months that I stayed by her bedside. Her struggle made me believe less in the neatness and finality of endings and more in love and sorrow. At one point, she advised me to "go places and have lots of fun." A day after her memorial, I drove 70 miles to my fiancs apartment in Monterey and signed up for scuba lessons with my diving instructor, Steve. He now motions forward; we've spent long enough in one place. Outside our wet suits the temperature is 55 degrees F. Even through neoprene that's a quarter-inch thick, I feel chilled. Long, slow kicks propel us between the giant kelp stalks. The exercise generates welcome body heat. My breathing, an act I've rarely noticed before, sounds uncomfortably mechanical through the hoses and regulator. Proving the bowling-bowl physics I learned earlier, I find that with each inhalation, I rise a few feet in the water column, and when exhaling I sink. Most bony fish possess swim bladders. Their nervous systems automatically regulate the amount of gas in the organ to keep them neutrally buoyant at various depths. How easy for the scaly Pisces to exist in this world, I think, as I inhale to sw im over a cluster of boulders. A pink patch of thumb-sized strawberry anemones blankets part of the outcropping along with a tapestry of ruffled seaweed. I notice that the shiny tissue of one reddish-brown algae glows iridescent blue when enough illumination strikes it. Dim shafts of light penetrate holes in the giant kelp's canopy, and gliding through sections of the forest, I recall when I was a teenager how the colored windows projected the morning light into church. Five different marine-research facilities dot the perimeter of Monterey Bay. If you could drain the bay, a topography easily dwarfing the Grand Canyon would emerge - the largest underwater chasm along the continental United States. It plunges to depths of slightly more than two miles. Upwelling water, rich in nutrients from the canyon's floor, once fed legions of silvery sardines and the nation's largest fishing port. Overfished, the sardines vanished after World War II. The scientists say, however, that these are still some of the planet's richest waters. And I can see that diving here in the kelp forest is like opening a vast textbook of marine biology. Steve turns and stops in front of me. Unknown to us, a five-foot-long spotted harbor seal has been slyly tagging along in our wake, its whiskered snout only inches from my yellow foot-flippers. The playful beast stares at me with unabashed curiosity. It nibbles on one of my flippers. Steve has said these local seals are harmless unless severely provoked. They're accustomed to divers and often approach just to have their bellies scratched. I suddenly laugh at the friendly white-and-gray dabbled face. The laughter jets out in a burst of bubbles through the regulator. It surprises both me and my underwater Dalmatian-like friend. It's my first true laugh in more than a year. The seal quickly darts a safe distance away from the disturbance. I watch the bubbles zigzag to the surface. The last 15 minutes of our dive, Steve and I spend examining different species of sea stars and crabs. Steve wears an orange sunflower starfish like a bonnet on his head. I momentarily tease a decorator crab that has camouflaged its exoskeleton with scraps of brown sponge. The seal now swims under us, looking up at these two funny mammals. I've convinced my fiancee to learn scuba in the evenings after her job. My brother is harder to persuade. The equipment reminds him too much of the respirators used during Mom's illness. The parallels have not eluded me either. Before starting our ascent, we search for a wide clearing in the kelp canopy so as to avoid entanglement. We climb very slowly, staying behind the trails of our bubbles. Breathe normally, I keep telling myself, holding your breath on ascent can damage your lungs as the water pressure decreases. On top again, Steve smiles, reaches over, and shakes my hand. "Well done," he says. The harbor seal has surfaced with us. I'm extremely glad I have a week of open-water diving left before reporting back to the newspaper. Many thoughts are racing through my mind. ... I'll have to tell my brother the seal's facial expressions remind me of his dog ... after our wedding, maybe my wife and I can go on a scuba honeymoon ... maybe, in a year or so, I'll leave my editing job and return to university to learn more about this ocean.