Claustrophobia and then the idea of mutiny gripped me as soon as I took one look at the 20-inch-high bunk space allowed me in the cabin I was to share with four others during a six-day "Sea Fari" cruise. Our voyage would follow the migratory Gray Whales off Mexico's Baja California coast.

The cabin was about the dimensions of our smallest bathroom at home. My immediate inclination was to jump ship. Before I flew out here I knew I would have to split a cabin. Also, I was told that the diesel boat, Finalista 100, was only 100 feet long. But this was the kind of thing that had led to the lifelong enmity between Lt. Fletcher Christian and Capt. Bligh.

All I needed to hear now was that one of the guys sharing the cabin with me was named Jonah. One already squeezed into a berth was Arthur Kaplan of Philadelphia. One of our cabinmates had already defected, he said. Dick Harrington of Toronto came in next with news of a second defection, leaving a choice of six bunks, one washbowl and approximately 8-foot-square standing space to three of us.

I still couldn't see how we were going to synchronize our elbows while brushing our teeth every morning, so I went up on deck to see if there was a taxi tooling around near the dockside.

Suddenly, there was a groaning and clanking of machinery and cries of impending movement. It was a minute after midnight.The Finalista slipped her last links with civilization, and I choked on the impulse to yell, "Stop, I wanna get off." We slid away from the glittering skyline of San Diego, from sight of the motel I had been eyeing, out past Point Loma Lighthouse and into the gigantic blackness of the Pacific.

I had a horrible presentiment that I was slowly being doomed to depict on a tinier canvas one of the most disastrous travel stories since the loss of the Titanic. But there was no turning back. I took a beer from the self-serve refrigerator in the ship's dining galley and contemplated my fellow voyagers.

I had expected the cream of the universities, or the Sierra Club, eruditelooking types who would be loaded with textbooks and scientific equipment. But this bunch looked no different from anyone you would see in the catalog line at Sears-Roebuck.

I didn't know then that I would fondly remember all 30 of them, and the Finalista 100 and its nine-man crew, probably for the rest of my life. And that we would later laugh at the inconveniences of the voyage, and marvel at the wonders of nature that Jacques Courteau would have given his eye-teeth to have filmed for his TV series, "Undersea World," but never had the luck to witness when he made one of his specials along the Baja California coast.

One of the fascinating acts of nature was the birth of a baby elephant seal for which the French underwater cameraman had waited two weeks in hope of filming. To the amazement of Dr. Theodore Walker, our guide and naturalist, who also had accompanied Cousteau, an elephant seal gave birth right in front of us when we visited a rookery on San Benitos Island, one of the stops on our schedule. The mother scattered all her neighbors to make room for her pup in the crowded colony.

But the highlight of the trip for four of us out whale-watching one morning in San Ignacio Lagoon -- the main destination of the nature cruise -- was the birth of a baby whale right under the tiny skiff in which we had been following the mother. Walker, an expert on the Gray Whale, knew of only four other recorded sightings of the birth of a Gray Whale.

The Gray Whales migrate to the lagoon from December through March. More than 10,000 journey to several lagoons in the winter to have their calves and to mate, the first half of a 10,000-mile roundtrip that last eight months, starting and ending in the Bering Sea between Alaska and Siberia.

All of us had made a sort of pilgrimage to see the final phase of this marathon life-cycle, picking up the southern route of the whales' migration just off San Diego, with sidetrips for nature walks on the offshore islands of Todos Santos, Cedros, San Benitos and San Martin along the Baja California coast. We went ashore by motorized skiffs lowered from the ship.

But the meaning of the voyage was every hit as sociological as ecological. There was no cruise director to "organize" games and no deck room to play them. Just a few fishing poles. There wasn't a swimming pool, either, although once we dove off the side into the chilling 65-degree ocean when Capt. John Koehler considered the anchorage safe from sharks and dangerous currents. But everyone seemed to have the time of their lives.

Not that it was all plain sailing. On the next to the last day, the sea was so choppy the milk ran out of my cereal bowl. I gave up trying to take a shower because the jet kept missing me.

One of two things can happen when you put 30 strangers together in a space 100 feet long by about 20 feet wide for six days, on a ship that has barely enough seats for them all to sit together at one time, in a dining room that also doubles as a lounge; sharing three toilets with washing facilities, plus two showers. Of course, we might have killed each other. But when the time came to part at the dockside, a generous hat went around for a very popular crew and there was much picture-taking and exchanging of addresses.

The whales had brought us together, and the memorable spectacle of the magnificent behemoths, close enough almost to touch, made the small inconveniences seem part of an epic voyage.

We had done something we would never think of doing back home, on the subway, in the street, or the supermarket -- we turned suspicious aloofness into friendship. Little cliques never formed because the cabins were too small for that kind of socializing. Although in fairness to H&M Landing, which operates the trips, I discovered later that many of the cabins were adequate and some had double beds for couples.

What little hardships were inevitable became a common bond -- something to joke about, even to be proud of having endured. Our skipper, whom we jokingly referred to as Capt. Bligh, prescribed "GI showers" for everybody: "Soap yourself and then a quick rinse. . . that way there will be enough hot water for all of you." Seasick cases must bow over the rail of the boat, or the ship's sensitive plumbing would go on the frits -- but we were warned to leave over warily on those dark nights in the Pacific where "man overboard" might never be found.

We had several gourmets aboard, but personally I found the grub nourishing and my appetite horselike. Dinner became a big social occasion. Afterward there were arch rivalries between checker players. And most evenings, Walker gave a slide show and lecture -- the most sensational of which was a shot of a trio of whales making love, a King Kong-like sexual feat that silenced the mutterers.

Walker is a gentle, patient, bearded man, a sort of ecological guru, who so deplored the destructiveness of vegetation by fishermen on some of the islands we visited, that he told us once: "I take a seasick pill when I come on land."

We all became attached to him, I did not flinch when he begged me to stand perfectly still while he photographed a huge, exotic spider that was crawling along my shoulder. "Is it poisonous?" I asked. It had a back encrusted like a brooch. He said he thought it probably wasn't. At the next bend he cautioned me against swimming in a river because of sting rays.

He taught us the names, peculiarities and amazing adaptabilities of flora and fauna that most of us would never see again. The point was, he said, not whether we could remember them all and classify them, but that he might enable us to see that the success of the ecology was our success.Hadn't the whale inspired us all?

"Arthur, you just stepped on a neat flower," he would say (the doc rated things "neat," "super" or even "superdeluxe," such as the spider that had crawled up my shoulder). Then he would deliver a ecology to the crushed flower during walks that sometimes went seven miles.

Most nights by 10:30, the Finalista was like a deserted ship: Everybody was in a bunk regenerating for a 6 a.m. breakfast and another walk with Walker.

We anchored for a good part of three days in San Ignacio Lagoon, an area about 21 miles long and 4 miles wide, and the most undisturbed of the three breeding grounds and nurseries of the Gray Whale. Occasionally, the leviathans would cannon three-quarters of the way out of the lagoon, exploding tremendous upheavals of water within good viewing distance of the skiffs that seated five comfortably at the most. But most of the time the mothers and their calves rolled alongside our flimsy craft, so close once that a woman reached out attempting to touch one. Their great tails "fluked" --a whaling expression meaning fanned --the picture-takers "ooooh" and "aaaah."

"I feel like a godmother," said Mary Cunningham, a San Francisco nurse, when the baby whale was born beneath our skiff, pools of blood coloring the lagoon, turning milky, as the other boosted the youngster on its back so it could take its first breath. (They weigh about 2,000 pounds at birth.)

At night, the lights of our anchored ship attracted great schools of fish, some of them so exotic that even the crew and Walker couldn't classify them. Darting after them were sea lions so funny and unafraid that somebody yelled, "Showtime!" and we all rushed out to watch their antics.

There was also the excitement of entering and leaving the lagoon mouth, a treacherous shifting sea bottom. Capt. Koehler had to wait for the right moment to give us a clearance of a few feet. The passengers looked on as the crew took stock of the situation, relishing the drama.

But the grand finale came off San Martin Island, the evening before we docked in San Diego -- when as many as six whales at a time surfaced in unison.Passengers perched for pictures on the roof of the captain's bridge while he steered just behing the fanning tails.

It was a fantastic voyage, and as somebody said: "There wasn't a Jonah aboard." FOR MORE DETAILS

There are a number of whale-watching cruises out of San Diego, ranging from several days to a few hours, but advance bookings are advisable. More information is available from the San Diego Convention and Visitors Bureau, 1200 Third Ave., Suite 824, San Diego 92101. Phone (714) 232-3101.

Additional details on next season's trips aboard the Finalista 100 can be obtained by writing H&M Landing, Emerson Street, San Diego 92106 (Phone 714-222-1144). The whale migration ends in late March. The $425, six-day cruise includes all meals. Air fare to San Diego is extra and arranged independently.