Highlights of a Baltic cruise

It was our brief, rain-drenched landing on the small island bird sanctuary of Stora Karlso that, as it were, separated the sheep from the goats. ''It's much drier later in the year,'' our young guides kept assuring us.

We believed them, but our Baltic cruise schedule was fixed and tight, and Stora Karlso was today, rain or no rain. It surged down our necks, soaked our cameras, squelched round our feet, and streamed (like maple syrup off a spoon) from the ends of our noses. And we wouldn't have missed Stora Karlso for worlds . . . would we?

I was going to say that this wet little adventure off the west coast of Gotland separated the ''trepids'' from the ''intrepids.'' But then I remembered that most of the 79 passengers aboard M.S. Lindblad Polaris could legitimately claim to be ''Intrepids.'' The Intrepids Club offers membership to anyone who has participated in at least one Lindblad ''tour, safari, or expedition'' (and has $25 a year handy for the fee).

Naturally, when Lindblad Travel Inc. (based in Westport, Conn.) starts up a fresh series of cruises, as it has this season round Scandinavian waterways in a newly renovated ship, Polaris, then Intrepids members (not to mention journalists; travel agents; public relations men; the ship's owners; assorted visiting dignitaries and well-wishers; and, of course, Lars-Eric Lindblad, the ebullient Swedish-American company president himself and his charming wife, Cary) will be given the first bite of the cherry.

The maiden voyage was probably not quite like any other of Polaris's now-regular spring and summer cruises in the Baltic (as well as in and out of the Norwegian fjords), but, in spite of the rain on Stora Karlso, the wind on Oland, the hail in Stockholm, and the snow in Helsinki - it was the week before the normal season begins - we got a pretty good taste of the high quality of this Lindblad offering and its very special blend of luxury and adventure, city and country, sea and port, nature and history.

The idea is to see the cities and islands of the Baltic from the traditional traveler's point of view, approaching each piece by its maritime front door instead of by the modern back door of rail, road, or air. Train stations and airports generally bring you by the least attractive route into a city. But arrive in Helsinki by ship, and you are immediately faced with a skyline that highlights some of the Finnish capital's impressive (if reconstructed) traditional architecture, and you can virtually step off your ship into a delightful, friendly, colorful fruit and flower early-morning quai-side market. In summer you can also buy fresh fish straight from boats moored alongside.

A short walk brings you to the center of the city; you avoid bus links through industrialized wasteland or the repetitive back streets of suburbia. The Lindblad Polaris cruises are so well organized that most of the actual sailing is done at night, and you wake up to the prospect of another excellent breakfast on board (the cuisine is first-class on this classless ship, particularly the generous Swedish smorgasbord lunches) and another day full of seeing the sights (generally by luxury coach).

As the Stora Karlso episode rather dramatically indicated, the sights you see on a Lindblad Baltic cruise are by no means just the typical and expected ones. Certainly in Copenhagen you see the ''little mermaid'' (who is much smaller and prettier than I expected) and the fantasy world of that marvelous, popular period-piece fairground, the Tivoli Gardens. In Stockholm or Trondheim (each cruise is different), you won't miss the famous and favorite sightseeing spots.

But Lindbladers (as they are rather inelegantly termed) are used to the idea that they will be taken to see remote colonies of guillemots perching on dangerous cliffs and wildflowers that grow nowhere else in the world but places like Stora Karlso. And they are used to climbing down into rubber rafts so that they can set foot in corners of the world that more conventional travelers pass by. And, intrepid as they mainly are, they are not to be put off by mere weather. After all, Lindblad organizes tours into the Amazon, into remote parts of Africa, up the Yangtze, into Antarctica, into the Galapagos Islands. Why should the Baltic be less of an expedition? Complaints were muted or humorous as the rain finally reached our skin, and there was a general air of having lived bravely as we returned to the anchored Polaris that morning.

The rubber rafts are used to reach the more difficult places, but the Polaris itself is a ship with a shallow draft and can explore where larger vessels can't. I asked Mr. Lindblad if it wouldn't be possible for a tourist to make the same journeys that he offers on the Polaris by using the regular ferries that ply the Baltic and the public transport and hotels available on shore. ''But think of the inconveniences of doing it all yourself,'' he answered. ''And it makes bad use of your time. Besides, it would cost you much more.'' He laughed. ''We provide a cheap luxury cruise!''

While its luxury is beyond question, its cheapness might just be a matter of opinion. In '83, the cruise has been expanded from eight to 17 days; prices per person in a double cabin begin at $3,520 and reach, at their most expensive, $5, 920. This does not include the air fare from and back to New York. Also, quite a heavy proportion of shore excursions carry a supplemental charge. The result is that Lindblad traveling tends to appeal to the wealthy. There were no children or very young couples on our cruise. Also, as Mr. Lindblad himself remarks, there is a quite high proportion of octogenarians among his clientele. But if this suggests inactivity, nothing could be further from the truth.

''They're only as old as they think they are,'' Mr. Lindblad said, and, although deck chairs are provided free, it wasn't just the cool Scandinavian spring which stopped people from lazing about; it was a very full program indeed. Relaxation was for evenings and nights!

Perhaps the most unusual aspect of the Polaris Baltic cruises is that they include the possibility of visits to three cities in the Soviet Union: Tallinn, Riga, and Leningrad. We went to Tallinn (where it didn't rain), which is ancient and very picturesque. It is the capital of Soviet Estonia. Mr. Lindblad thought people might be put off by this side of his itineraries. He was wrong. Perhaps the sense of security offered by his exclusive little ship encourages them to feel this might be an ideal way of glimpsing behind the iron curtain. The day in Tallinn was frustratingly short, but it added an intriguing note of contrast to the cruise.

The city is a center for industry, but it is also something of a historical showpiece, with its old and attractive medieval houses and streets carefully preserved. Since the Intourist guidebook states that 40 percent of Tallinn's buildings were destroyed by the Nazis, there must have been considerable rebuilding since the war. The coach guides were friendly and efficient, and although the officials at passport control were as sullen and dilatory as you can imagine, one boy, on duty all day at the Polaris gangplank, eventually melted into good humor; he was human, after all.

We saw churches, and Peter the Great's Kadriorg Palace, and gazed down at a vast and proudly presented modern stadium for singing festivals. We were shown the (now sadly neglected) sailing center, site of the 1980 Olympic regatta. And (rather too briefly) we were allowed to wander about in an excellently set out open-air museum at Rocca-al-Mares, which has an impressive collection of peasant architecture, barns and houses, mills and smithies brought from all over Estonia. This kind of planned nature park, preserving rural buildings and practices from the past, is something Scandinavians generally do particularly well. We had earlier been treated to Walpurgis Night celebrations (dancing, people on horses walloping barrels with sticks, a bonfire, and other such cheerfully primitive rituals) in Stockholm's Skansen park. On the Aland Islands we saw yet another open-air museum.

The final memory of Tallinn, however, was not so much old and pretty as modern and strangely formal. We were given a meal (with caviar) high up in a hotel (entry restricted) and were serenaded by well-organized folkloric musicians. I kept wondering, however, as this scrupulously proper and oddly cool piece of hospitality progressed, if something I had been told by a teacher in Helsinki the evening before were true.

There, in the Finnish capital - in a charming seafood restaurant ''of international class,'' the Havis Amands - we had gourmandized on sensitively prepared pikeperch, garnished with a delicate concoction of finely shredded and sauteed horseradish, preceded by a shellfish soup that was of other-worldly class. During the dinner conversation the teacher mentioned that a taxi driver had told her that at present in Tallinn (where some Finns like to go for an escapist weekend) there was no butter and no meat. . . .

I looked down at the rooftops of Tallinn, making a dense pattern below us, and mused on the large contrasts simplistically apparent only to whistle-stop tourists. . . .

There is no way in which I could include every item of the voyage in this short article. Tallinn and Stora Karlso provided their own kind of unusualness. Other high points for me were a visit to the house designed for himself by the great Finnish architect Eliel Saarinen. Hvittrask, as it is called, was built at the turn of the century, a warming and human combination of the modern and the natural, of artistic originality and imaginatively adapted traditions. Then there was the extremely primitive opposite, at the southern end of the island of Oland. This is an excavated and now partially reconstructed prehistoric ring fort, or fortified village. The young man who hastily showed us round Eketorp had actually lived in one of the cramped stone- and turf-thatched houses for a couple of weeks. It is hardly luxury accommodation. The peasant society that inhabited this circle of stone walls formed the first settlement with row-style houses in Sweden.

Two other aspects of Oland (which is linked to the Swedish southeast coast by the longest bridge in Europe) which fascinated me, were the wide, flat stretches of the Stora Alvar, which is the largest tundra in Europe except for Siberia, a treeless limestone steppe that our coach guide suggested was best explored by walking over it for three or four days. We stepped out of the coach for five minutes and gazed. Golden plover and lapwing wheel over the Alvar steppe.

The great Swedish botanist Carolus Linnaeus found all kinds of flora in this bare country, which, though it only has a few inches of soil over the rock surface, is at certain times of year smothered with heather and thyme in bloom.

My cruise highlights will inevitably be different from those of other travelers. Perhaps theirs would include a visit to a Swedish glass factory, to the shopping center in Copenhagen, to the holiday resort of Visby on Gotland (a kind of unbelievable Disney World inside a very impressive two-mile circuit of limestone town wall built at the end of the 13th century). By opting for additional stopovers in Stockholm or Helsinki or Copenhagen, you can take in much more of these places, their great museums and parks and botanical gardens.

We ended in Copenhagen, and I was glad of extra time there, though the scheduled tour had shown us a great deal of the city in a short day, including the wonderfully sited Louisiana Museum of Modern Art, lunch in a restaurant one could safely recommend to a king - the Sollerod Kro at Holte (chocolate cake, decorated with slices of kiwi fruit, surpasses the wildest dreams) - and, in passing, glimpses of Denmark's stunning beechwoods, with, at that time of year, expanses covered with millions of white wood anemones. . . .

I suppose I am now a persuaded Lindblader. I certainly toy with the unrealistic notion of a Lindblad cruise in Antarctica one of these days.

True travelers aren't put off by mere climate.m