WORLDS WITHIN WORLDS ABOARD THE ALTAIR

The beam of light from the pickup boat, bobbing like an oversized flashlight in the hand of a child, knifed through the blackness. It illumined two ships that did not want to pass in the night.

The scene evoked a nautical Mutt and Jeff: the towering 666-foot-long MormacAltair merchant container ship trying to rendezvous with a tiny harbor craft. The task was to return to shore, to ''put down onto the deck,'' the New York harbor pilot who had guided the Altair out of port and onto the open ocean 10 miles beyond the light-bedecked Verrazano-Narrows Bridge across New York harbor.

Putting the pilot down from the larger to the smaller ship would be no easy task. Spray from the choppy seas caked layers of ice over the bow of the pickup boat. The air temperature was 18 degrees F., and the entire operation would occur at a speed of 12 knots (about 14 miles per hour).

A wood-slatted rope ladder dangled from the Altair's main deck to within three feet of the water.

Without a life jacket, and dressed as if ready to step out on the town (shirt and tie, trench coat, dress slacks and shoes, no hat or gloves), the harbor pilot descended the 20-foot ladder, timed the rise and fall of the moving vessels, and hopped over to an outstrectched arm. He paid no heed to the ice-covered deck; his only concern appeared to be not scuffing his shoes on the railing.

My four-day coastal cruise on a US merchant ship had begun. From the outset it was clear I was a landlubber, and Capt. Turner Augustus (Gus) Evans's greeting only confirmed this fact: ''Welcome aboard! Always nice to meet the walking cargo,'' he said good-naturedly. There was no concealing the sea-dog glint in his smile. Introducing nautical neophytes to the crew was something he was not only an old hand at, but something he clearly relished.

''Walking cargo'' is Captain Evans's phrase for passengers. Many US merchant ships have tourist-class cabin -- accommodations for seafarers who pay their own way. Demand for the cabins is so great, says Dennis Crowley, manager of passenger operations for Moore McCormack Lines Inc., owners of the Altair, that reservations must be made almost a year in advance. That popularity grossed $1.6 million for Moore McCormack in passenger revenues last year on its 14 ships.

My first impression as ''walking cargo'' was a salt-filled dose of doubt. How can flesh and bones relate to all this steel?

''Steel everywhere on this ship, don't feel human after a while,'' intoned crew member Sandy, as if to confirm my apprehension.

Haitian by birth, Sandy calls Brooklyn home eight months of the year. There he runs his own small cement contracting company, but business is bad in the winter and the cold pushes him toward the Caribbean. ''Might as well get paid while I'm going that way,'' he says.

The Altair is more than two football fields long. It's 75 feet wide and 42 feet deep. It carries 520 8-foot-by-10-foot-by-40-foot metal containers stacked eight high (five high in the hold, three high on deck) and cinched down with cables like some tightly packed string of rectangular sausages. The containers are carefully weighed and positioned by computer so as to maintain an even keel and avoid tipping in rough seas. A single container can hold up to 16 tons. The ship also carries three 20-ton cranes, 12 eight-ton booms; all lengths of cables , railings, nuts, bolts, girders, a five-story pilothouse, smokestack, anchor, and anchor chain.

People accommodate to the metal, not the other way around. A cargo ship's purpose, from bow to stern, is hauling for revenue.

As if to emphasize the primacy of inanimate steel over animate flesh, the Altair was hauled into drydock in 1972 and split in half. One hundred fifteen feet were added to her midsection, doubling her container-carrying capacity. The cost for the stretching -- ''slenderizing,'' as the crew jokingly calls it - was more than the original price of the ship.

As time passes on this trip, the ship takes on a rhythm of its own. ''You learn to love the sound of a ship at sea,'' says third mate Bill Linquist. ''When that happens you'll know you're going to enjoy all this.'' He gestures toward the expanse of deck, rigging, and ocean from his position at the engine controls in the pilothouse. ''The sound of the money I make is good too,'' he adds, smiling.

Familiarity with the ship did cause the steel to mellow. A sense of discovery replaced the alien unfamiliarity of the ship's architecture. Caverns within caverns opened up. Some hospitable, especially the officers' mess; some inhospitable, such as the cargo hold where 800 tons of castor oil were stored.

Nowhere is more inhospitable than the engine room.