Nearly everyone these days seems to have been to China, or is going to China, or might like to get to China if it were not so complicated and expensive. Not much can be done about the expense; it is a seller's market. But one way to simplify the journey may be to go by cruise ship.

It can be done. On April 16, a Greek cruise liner, the Aquamarine, began 14-day cruises between Hong Kong and Kobe, Japan, with stops at Canton, Shanghai, and Hsinkang (for Peking).

The Aquamarine will be shuttling back and forth on this route every two weeks between now and mid or late December - and if all goes well, will continue through 1980. All did not go well, however, on the Aquamarine's maiden voyage, and there are serious bugs to be ironed out if it is to be a pleasant and convenient way to "do" China.

You do get a frustratingly brief but fascinating kaleidoscope of irrigated paddies, oriental gardens, swarms of bicyclists, men and women with shoulder-poles, pigtailed girls in Mao jackets, doll-like children, and friendly greetings everywhere. River and harbor traffic is equally absorbing: fishermen in sampans, junks with red and brown sails, and tugs pulling chains of barges - sometimes 10 or a dozen barges long.

A total of about six days is planned ashore, and will no doubt be delivered if the Aquamarine can stay on schedule (as it did not on its maiden voyage). In addition to Peking, Shanghai, and Canton, a side trip to Suzhou (Soochow) or Wuxi (Wushi) is scheduled, as are trips to the Great Wall and the Ming tombs.

Itineraries ashore are prepackaged by the official China International Travel Service. Very little do-it-yourself travel is permitted. You see what the Chinese think visitors want to see - or what they want visitors want to see - rather than what you may really want to see. One sometimes feels he has had enough of People's squares, People's hospitals, People's parks and People's department stores.

But there is no way anyone can conceal the magic and novelty of China. The people themselves are China's great triumph.

A cruise ship as a way to visit China gains force and logic from the admitted mediocrity, or worse, of many (though not all) Chinese hotels, trains, and buses.

"The Great China Cruise," as it was billed, was to have been an opportunity to see the country with "all the amenities of a luxurious liner . . . available" as your hotel, dining room and mode of transportation.

Unfortunately, this is not yet true. Efforts are being made to provide luxury, and sometimes it works. But on our voyage there was trouble with the water supply (availability, not quality), trouble with the lights, trouble with the ventilation, no laundry service, and the food from Hong Kong and China varied from good to ordinary. Much of the service from the Greek crew was good, though some was surly. Many cabins were spacious. The ship, however, was inexcusably dirty, soot from the smokestack frequently littering decks and chairs.

Scheduling foul-ups cut our day in Canton in half, and wiped out Soochow. A visit to a Shanghai carpet factory was duplicated in the next city. And because no space was available in a Peking hotel, passengers had a two-hour commute, each way, from Tianjin (Tientsin) to the capital and then another two hours each way to and from the Great Wall. We got up at 4 a.m. and returned to the boat after 9 p.m.

Some staff resigned over working conditions. But for many of the rest, the China mystique overshadowed and obscured inconveniences the way mist veils the mountains of this fascinating country - both in real life and in oriental paintings.

A bright spot was the nightly entertainment in the lounge, featuring Marcia Singer, a talented chanteuse from San Francisco with a master's degree in psychiatric social work - a talent which came in handy in dealing with irate passengers.

Philip Kavounides, the 30-year-old scion of a well-known Greek shipping family, with 5 1/2 years' experience, is the man behind the "Great China Cruise." Because most other China tours are solidly booked, and because, although other cruise ships may touch at China, he has a monopoly of the coastal run, Kavounides can charge clients $1,595 to $3,500 per person, double occupancy required.

That amounts to between $228 and $500 a day for a couple, and air fare to Hong Kong or Kobe is additional. The low figure is steep, considering that luxury accommodations are not yet being provided. The top rate seems out of the ball park. Shore excursions and the cost of the China visa are included.

If you decide to come, have your travel agent check carefully the readiness of the ship: ventilation, hot water, cleanliness, laundry, sports facilities and location of cabin. (Under no conditions take a cabin below Ivory Deck.)

The Aquamarine is an 11,000-ton, 351-passenger vessel originally built 17 years ago to accommodate 270. Kavounides needs a newer ship, and may in fact get one.

Bring binoculars, camera and lots of film. There are charming picture opportunities at every hand. A tape recorder will also provide valued mementos. Come early, and enjoy at least a few days in Hong Kong, one of the most fascinating cities in the world. Hong Kong has excellent hotels - the Hilton, for example. If you begin your cruise in Kobe, shake off jet lag at nearby Kyoto, Japan's ancient capital with its famous temples and gardens. Kyoto is a 40-minute train ride from Kobe.

Pan Am, Northwest Orient and Japan Air Lines fly to Tokyo daily, and connect for Hong Kong. It is a long, hard flight which one does well to break. (Northwest stops in Seattle, JAL in Anchorage.)

If you are overnighting in Japan, remember that downtown Tokyo can be two hours away from Narida Airport in heavy traffic and seriously consider staying one night at the Holiday Inn or some other airport hotel. Check weather records, and the climate in Hong Kong can be very different from Peking. CAPTION: Illustration, no caption