A cruise on the Mississippi River is much like an oceangoing cruise, except you can watch the scenery on shore passing by and, since the ride is very smooth, you are very unlikely to get seasick. Like other cruises, too, you can sit on deck and enjoy the sun and the water views or duck inside for a variety of planned day and evening activities -- such as bingo, cabaret shows and dancing. Tours are offered regularly to historic river towns and plantations and Civil War battle sites. WHEN TO GO: Both the 180-passenger Delta Queen and the 400-passenger Mississippi Queen, sister ships of the Delta Queen Steamboat Co., offer two- to 12-day cruises on the Mississippi and Ohio rivers year-round. Departures (depending on the date) are from New Orleans, Memphis, St. Louis, Cincinnati, Nashville, Pittsburgh, St. Paul and Chattanooga. The Delta Queen's longest cruise in 1988, 12 days, departs Pittsburgh June 5 for the home port of New Orleans.

The 140-passenger New Orleans, operated by American Cruise Lines, sails the Mississippi in spring and fall. It offers two seven-day itineraries -- a round trip between New Orleans and Vicksburg and a one-way trip from New Orleans to Memphis or back. Unlike the two Queens, the New Orleans has an electric engine, not steam-powered paddle wheels, though it was built to resemble a steamboat.

ACCOMMODATIONS: On the Delta Queen, cabins are small but reasonably comfortable. Some have double beds, many have twins. Ours had bunk beds. All rooms have a private toilet, shower and air conditioning. We had sufficient storage space. All rooms are above the water level and open onto one of three decks. Because of the boat's age, passengers are warned not to drink water from the tap in their rooms. Instead, pitchers of fresh water and ice are delivered at least twice daily. There are no radios, television sets orphones in any of the cabins, and no desk or chairs in ours. To relax, we found a seat on deck or in one of the very nicely appointed sitting rooms.

The Mississippi Queen, commissioned in 1976, has larger cabins equipped with either full-sized or twin beds. All have private baths, and many have private verandas. However, some cabins have inside access only with no windows. Also a newcomer, the New Orleans offers all outside cabins with picture windows.

DIVERSIONS: Our cruise took the theme "Rhythm of the Rivers," and we were treated on three successive nights to an after-dinner Dixieland jazz concert, a banjo player entertaining with songs of the river, and a bluegrass concert. Other scheduled pastimes: kite flying from the stern, an afternoon singalong, a chance to play the calliope, bingo, a napkin-folding lesson, the captain's champagne reception and tours of the engine room.

I gladly would have done without any of them in exchange for a series of on-deck talks about the river -- for example, its history, present-day commerce, navigation problems and flood control efforts. The lack of such talks was a big disappointment. Some lectures are offered on longer cruises.

For exercise, passengers can stride the decks. Eleven laps equal a mile. There also is a cluster of exercise bicycles on deck facing over the bow. I pedaled past Baton Rouge through rain and wind.

Because of its larger size, the Mississippi Queen offers many more amenities. It has a well-equipped exercise spa and sauna, where massages are available. A large hot tub bubbles on the top deck, surrounded by plenty of lounge chairs for sunning. There's a good-sized movie theater, which on a recent cruise was presenting the classic "Showboat." AMBIANCE: The Delta Queen shows some of the frailties of old age, but its public rooms retain the stately dignity of a fine library. The boat is much more open to the river than the newer boats, having what appears to be more deck space despite its smaller size. Far more luxurious, the Mississippi Queen seems to enclose its passengers in glass, separating them from the river. You know you are boating on the Delta Queen. On the Mississippi Queen, you might think you have checked into a glossy new hotel that happens to be sitting on water. FOOD: The food aboard the Delta Queen was quite good. Much of the menu reflected New Orleans' Creole and Cajun heritage, with plenty of fresh fish and spicy dishes if you wanted them. Portions were moderate, suggesting the chef prefers quality over quantity. The waiter points out, however, that you can ask for bigger servings. Breakfast and lunch offered a choice of buffet or served meals. COST: A two-night cruise on the Delta Queen ranges from $282 per person (double occupancy) to $728, depending on the quality of cabin. A three-night cruise, similar to the one I took, is $429 to $1,101 per person. A 12-night cruise is $1,692 to $4,368. Fares on the Mississippi Queen are about the same, although it has an additional cabin category that is more expensive.

Rates on the New Orleans for a seven-day cruise range from $1,575 to $1,960 per person (double occupancy).

Additional costs on our Delta Queen trip were air fare to New Orleans, shore excursions ($5 per person for Houmas House and $17 per person for St. Francisville), beverages and tips. Suggested tipping was $2.40 per person a day for the waiter; $1.15 per person a day for the busboy; and $1.90 per person a night for the maid. A 15 percent tip was added to all beverage service.

The Delta Queen and Mississippi Queen offer packages that include air fare and accommodations in port cities. In New Orleans, the company operates a very nice small hotel in the French Quarter called the Maison Dupuy, where passengers on a cruise package stay. It has a proper French Quarter interior courtyard shaded with tropical plants. INFORMATION: Delta Queen and Mississippi Queen: Delta Queen Steamboat Co., 30 Robin St. Wharf, New Orleans, La. 70130, 1-800-543-1949.

The New Orleans: American Cruise Lines, One Marine Park, Haddam, Conn. 06438, 1-800-243-6755.