By 1982, five brand-new cruise ships valued at a total of more than $500 million will be sailing the waters of the Bahamas, Bermuda and the Caribbean. There will also be four entirely new cruise companies offering their services to those who want to vacation at sea.

Why this kind of investment at a time of recession, fuel crunch and dwindling dollar? Most cruise line executives answer that they've run into economic storms before and have managed to stay afloat. It's a matter of optimism and long-range planning.

The lines are actively preparing for the next generation of cruise passengers of the '90s and the year 2,000, only 20 years away. And they are willing to spend millions to ensure full steam ahead.

Each new ship, except one, is being built from the keel up at various European shipyards.

One of these super deluxe liners will be sailing from New York harbor in early 1982. Home Lines, owners of two ships, the Oceanic and Doric, is building the Atlantic with a price tag of $100 million at the shipyard of La Seyne-sur-mer near Toulon, France. The 30,000 ton vessel will carry 1,150 passengers, 75 percent in outside cabins, and will cruise to Bermuda.

There is already talk that Home may sell the Doric soon after the new ship is launched. If that happens, there are plans already on the drawing boards for another new vessel at a price tag to exceed the Atlantic's cost.

Down in Miami, Carnival Cruise Lines is adding to its current fleet of three ships, the Carnivale, mardi gras and Festivale. When asked the cost of the new ship, officials hesitated but did admit it will be in the range of $100 million or more. The new vessel, the Tropicale, is under construction in Denmark's Aalborg shipyard. Touted as the ship of the '90s, it will have 500 cabins, a crew of 500 and feature king-size beds, color TVs and stereos in each cabin. The Tropicale is expected to sail in February, 1982, on seven-day Caribbean cruises from St. Thomas, not Miami.

Sitmar Cruises of Los Angeles is rebuilding a ship from the hull of the Principe Perfeito, a Portuguese vessel that the line bought last year for an undisclosed sum. Sitmar is spending between $40 million and $45 million to reconstruct the ship. The new liner, the Fairsky, was to enter service in 1981, joining the Fairwind out of Port Everglades, while the line's other ship, the Fairsea, continues to sail from California. But the 23,000-ton Fairsky is behind schedule and won't sail until 1982. It will have between 400 and 450 cabins.

Another new entry is the still-unnamed vessel being built by Royal Caribbean Cruise Line of Miami at the Wartsila Shipyard of Helsinki, Finland. The $100-million, 31,000-ton ship will enter weekly Caribbean service in late 1982 from Miami, with a capacity of 1,400 passengers. This cruise line is the one that pioneered the practice of cutting a ship in half and enlarging it. The Song of Norway underwent the revolutionary operation last year, and more recently the line's Nordic Prince was lengthened in the same Finnish shipyard.

Following that example, Norwegian America Cruises is now adding a new sun deck and luxury-type suites to the Sagafjord somewhere in Europe at a cost of $12 million. The ship's capacity will go from 475 to 503 passengers.

Also scheduled for the same surgery is the Royal Viking Star of the San Francisco-based Royal Viking Line. They will put the vessel into drydock at a shipyard in Bremerhaven, Germany, next August through December, and extend it from 583 to 674 feet, increasing tonnage to 29,000 tons and allowing for expanded public rooms and passenger capacity. Ten new penthouse suites with private verandas, a new Sky Deck Lounge and a second swimming pool will be added at a cost of "millions."

In keeping with expanded vessels and new ships is the double entry of a new shipline that's building a new liner. It's Scandinavian World Cruises with offices in Miami. The company is a division of DFDS, a part of the Lauritzen Group of Copenhagen, Denmark. The DFDS Group is one of the largest operators of car ferry service in Europe. And that's what the new company will be doing on the U.S. East Coast. Starting next January or February, car ferry service will be scheduled three or four times a week between Freeport, Grand Bahama Island, and Miami. (The vessel was not announced.)

The line is currently building a $100 million vessel, the Scandinavia, a 1,000-passenger ship capable of carrying 400 autos. Service will be five days a week roundtrip, sailing 70 times a year between New York City and Freeport, beginning sometime in 1982. The ship is under construction in the French shipyard of Dubigeon-Normandie.

A second new company, Western Cruise Lines, a division of Eastern Steamship Lines, Inc., begins cruise servive Nov. 14 from Los Angeles to Ensenada, Mex., featuring both three- and four-night sailings. The ship is the Azure Seas (formerly Paquet's Calypso). Western will be doing essentially what Eastern now does so successfully out of Miami on three- and four-night trips to the Bahamas at relatively inexpensive prices.

Financial considerations have delayed plans by United States Cruises Inc. to take the S.S. United States out of her Norfolk, Va., drydock and rebuild the vessel for regular cruises from the West Coast to Hawaii and other ports around the world. It is 990 feet long and would carry about 1,200 passengers.

United States Cruises, which has paid the Maritime Administration a non-refundable deposit of $2 million toward the purchase price of $5 million, has been given an extension until next March to pay the balance. According to a spokesman for the firm, it has already spent an additional $3 million for architectural, legal and other expenses, and recently expanded construction plans for the 53,329-ton ship which will involve increased costs and thus necessitate additional financing.

Sale of time-sharing vacations aboard the S.S. United States are continuing, the spokesman said, but advance payments from passengers who sign up for priority bookings and discounts over a 20-year period were never expected to finance the entire cost of refurbishing the vessel. The firm is also contesting a suit filed against the Maritime Administration by an unsuccessful bidder who seeks to prevent the government from turning the ship over to the United States Cruises, the spokesman said.

Already in Hawaii service is the American Hawaii Cruises' Oceanic Independence , which became a vessel of American registry last June and began sailing from Honolulu on weekly inter-island cruises. The ship was originally launched in 1951 as the S.S. Independence .

The increased capacity already available in the cruise market and the promise of more berths to come have caused concern in some industry circles, and a new discount fare designed to help fill up cabins on one giant new vessel sailing out of Miami has disturbed a few lines.

The S.S. Norway -- formerly the famed France -- has been making quite a splash since her recent debut. With an additional 2,000 berths aboard the new ship to market, the successful Norwegian Caribbean Lines decided to introduce a special "Sea Saver" fare until Dec. 14. NCL operates four other vessels. Actually, "Sea Saver" doesn't guarantee the passenger a berth on the Norway, but the possibility is certainly there.

Here's how the plan works. The fare is $499 per person for inside cabins and $549 for outside ones. Interested persons can make reservations two to four weeks prior to sailing. The final payment must be made in full within seven days after booking the trip.

The fare applies only to the cruise, based on two persons to a cabin (double occupancy). It does not cover port charges, transfers to the ship or air travel. The line's air/sea program cannot be used. The passenger is given his or her preference for the weekend sailing wanted. The line, however, reserves the right to assign the ship and cabin, according to space available, after payment is received. Only a limited number of cabins are available at "Sea Saver" fares, and the line has the right to limit the number of cabins on each ship for each weekend sailing.

How do competing lines feel about NCL's new discount fare? Will it touch off a fare war? Hardly, say officials queried, but some lines aren't too happy, either.

Carnival Cruise Lines, also of Miami and a big operator of seven-day Caribbean cruises, feels that the prospective passenger, with the help of a smart travel agent, should shop around for a cruise and compare prices. Bob Dickinson, senior vice president of sales and marketing for Carnival, said that, based on minimum air fare available within 30 days of departure and assuming that a travel agent books a minimum guarantee with Carnival, the total air/sea costs are $24 to $344 per person less than the "Sea Saver."

"Minimum rate guarantees are available on a number of Carnival sailings now," said Dickinson. "About 80 percent of the time, clients end up with the better than minimum rate cabins. And the passenger knows in advance the ship, itinerary and sailing date before paying and doesn't have to worry about getting an airline seat at the last minute.

Still another Miami-based line, Commodore Cruise Lines, is "sitting back and looking at what will happen," according to the line's general sales manager, David Y. Levene.

"There's an over-supply of berths out of Miami. The cruise industry continues to experience peaks and valleys. NCL beds added by the Norway in the face of the current economy was bad timing, but how could the line anticipate this,"Levene said. He added that "if necessary, we would match the new promotional fares."

An interesting view was taken by Costa Cruises, which recently repositioned its World Renaissance from Miami to San Juan. The line's senior vice president, Paul Duynhouwer, said:

"We were among the first to see the dangers of new tonnage in the Miami market and took steps to maintain our position in San Juan. In May, we came out with a very attractive introductory offer for the seven-day World Renaissance sailings from San Juan, anticipating some softness in the market."

Even before the "Sea Saver," Holland America Cruises was promoting a "fly free" feature with early November cruises out of Miami, and according to the line's president, John Berry, the line has publicly announced guarantees of published cruise rates (also for the 1981 world cruise) against any unexpected increases or fuel surcharges to April 13, 1981.

Clearly unhappy about the new fare is Royal Caribbean Cruisee Line of Miami. The line dismisses it as another form of discounting which they say they're not willing to match.

And what is the verdict so far on "Sea Saver" at NCL? Officials maintain that it is proving very satisfactory and accomplishing what it's supposed to do.

This new fare points up another trend in the cruise business, the direct result of the current recession and the topsy-turvy dollar: late reservations. rMore and more prospective cruise customers are waiting later and later to make plans. The discount fare takes this into account by allowing plans to be made two to four weeks prior to sailing.

There's no doubt that advance bookings of six months to a year are fading. Most cruise lines queried felt that the passenger who applies late stands a very good chance of getting aboard. Accommodations, however, might not be exactly what is wanted. Carnival Cruise Lines disputes this and feels that the late booker may well end up with something better than expected while Paquet French Cruises deliberately advertises late (after Labor Day) to accommodate the late planner.

The lines have become more sophisticated in their approaches to marketing and public relations, especially when a problem occurs, as in two recent cases. a

First, Bahama Cruise Line's Veracruz was en route from New York to Canada for a series of sailings when her boilers conked out near Staten Island. All passengers were given free drinks, entertained, and promised refunds. After the ship was towed back to New York, everyone received a refund check or voucher before debarking. They left happily. Then, last month, the Norway lost all power near the Caicos Islands in the Caribbean and remained for 19 hours without air-conditioning, refrigeration, hot food or functioning plumbing. When the ship was able to return to Miami from the aborted cruise, all passengers were given full refunds of their fares, plus the offer of 50 percent off on any NCL seven-day cruise purchased within a year.

And that's good cruise business!