Cruising the spectacular Panama Canal

Cruise ships, like birds of migration, follow the sun and the warm weather. You can avoid hot summers at home by cruising in Alaskan or Scandinavian waters. During the cold season, cruise ships will gladly take you to the Caribbean or the South Pacific. The choice is yours.

There are literally hundreds of cruises to choose from. To my mind, the best buy in winter cruises is a trans-Panama Canal cruise. Most ships running it start out in Fort Lauderdale, Fla., and end up in Los Angeles or San Francisco, or the reverse. In between, you sail through the Caribbean, with several stops and shore excursions in foreign countries. After transiting the canal, you have a chance to spend a day in two of the three cities on the Mexican Riviera; Acapulco, Mazatlan; or Puerto Vallarta.

The main attraction, the piece de resistance, is the transit through the Panama Canal. It takes a cruise ship eight hours to get from the Atlantic to the Pacific, 50 miles of lake and canal.

Starting at the city of Colon, the ship travels for seven miles before entering the triple Gatun locks, which elevate it 85 feet into Lake Gatun. The canal and its locks are a wonder of engineering, especially if we recall that they are more than 70 years old and function the same way they did then, with only minor changes. The lock gates are as high as an eight-story building. It's an awesome sight to watch them open and close.

The day a cruise ship transits the Panama Canal - and most do so during the daylight hours - even the most inveterate late sleepers are up early. A scramble is on for the best club chairs in the top lounges. Positions are staked out on all decks, and photographers young and old are full of expectations. They will not be disappointed.

Most of us became conscious of the canal only in the late 1970s at the time of the negotiations for the transfer of the Canal Zone from the United States to Panama. Yet Panama and the canal have a checkered and colorful history (see accompanying story).

Present-day cruise passengers view with awe the narrow locks and the expertise with which ships are maneuvered through them. There are but a few feet to spare when the Royal Viking Line ships or the Queen Elizabeth 2 is passing through. Supertankers or larger aircraft carriers cannot make it - hence the diminished value of the canal, according to some experts. The ships are pulled by cables attached to small locomotives called ''mules,'' on the two shores. It is all coordinated by expert pilots and computers.

As the ship progresses through the canal, the scenery is constantly changing. In the locks there is much activity. The bells on the little locomotives are signaling to each other; you see the engineers adjusting the cables as they climb the steep inclines toward a higher level. On one side there is a shaded stand for landlubber tourists. On the other shore, there are military compounds and well-maintained repair shops and residential buildings. A little railroad hugs the coast and chugs along. The Pan-American highway snakes its way almost parallel to the canal. A bridge opens to let ships through.

Aside from the obvious excitement of transiting the most fabulous canal in the world, there are many other benefits to this cruise. On the Caribbean side, a frequent stop of many cruise liners is St. Thomas, a tax-free shopping center where English woolens, Danish porcelain, Swiss watches, and French perfumes compete for your dollars.

Curacao, in the Dutch West Indies, is another bargain shopping stop. Here women's wear is fabulous, especially beach and cruise wear. Yard goods for those handy with the needle come from Europe and Asia. Men's guayaberas (short coats made of light material) abound in all colors, styles, and sizes.

It is a good idea to pick a cruise that stops at Playa de Carmen, opposite Cozumel on the eastern shores of Mexico's Yucatan Peninsula. From here, organized shore excursions take you to the fabulous archaeological sites of the ancient Mayas, those intellectuals of the pre-Columbian civilizations. Chichen-Itza with its Observatory, Kukulcan's Pyramid, the Temple of the Warriors, and the sacred cenote (well) will leave you breathless.

Uxmal, the thrice-built ceremonial city of the Mayas, is another worthwhile excursion; the Magician's Pyramid, the Nunnery, and the Governor's Palace are exquisite in their ornamentations. Tulum, to the south, is the only seaside city of the Mayas. It offers a more leisurely trip, with lovely views of the ocean under deep blue skies.

Cartagena, in northern Colombia, is a combination of a modern city and old colonial glory. It was here that Spanish ships used to rendezvous before taking their treasures home. The old fortress of San Felipe still stands, with walls up to 50 feet thick. It is quite a climb up there in the heat of the day, as it is to the restored monastery of La Popa. The church of San Pedro Claver, patron of slaves, is well worth seeing.

Colombia is of course the source of the best emeralds, but beware: Don't buy emeralds from street vendors! Another attraction is the handwoven textiles, shawls, and molas, those hand-stitched, reverse-appliqued cotton panels originally made by the Cuna Indians of the San Blas islands off the Panamanian coast.

Mexico is a shopper's paradise. No other country offers the variety of goods in leather, copper, silver, ceramics, woods, textiles, and glass. Onyx carvings can be of the ''el cheapo'' variety, or they can be exquisite. In reputable shops the artistry is of high quality. Depending on your criteria, you can buy a Mexican wedding dress, full of lace, ruffles, and flowery embroidery, for about clothing, Puerto Vallarta and Acapulco are better than Mazatlan. Acapulco has the largest number of shops and selections.

In general, the Mexican Riviera is more attractive for shopping than eastern Mexico, which is known for its pre-Columbian cultural heritage and artifacts.

Most important, however, is careful shopping for the best cruise package. There is a veritable maze of ever-changing air-sea deals and bargains. By all means talk to friends who have sailed on the ships you're considering. This newspaper once called the Norwegian Royal Vikings ''the Cadillacs of the cruise ships,'' and they still are. I find the QE2 a lovely ship, but too large for cruising. Other ships that receive much praise are the Sagafjord and the Vistafjord. All have trans-canal cruises, as do the Princess and Holland America ships. For other possibilities, and there are many, consult your travel agent and cruise magazines.

Whichever ship you take, rest assured that a trans-canal cruise will be an unforgettable experience.