The placid aquamarine sea glints in the Caribbean sunlight. Small waves roll in gently toward a wide sandy beach. Sailboats move lazily just off shore. But a viewer admiring this colorful scene may still be at home, rather than far away on vacation, watching a videocasette guided tour.

The latest idea in tourism is travel videotapes. And an increasing number -- from a drive around Hawaii to a look inside an Egyptian Pyramid -- are being marketed, both for rent and for sale, in some video stores, bookstores and record shops.

Currently the tapes are not being carried by a large number of outlets in this area, and those that do stock them generally have only one company's product. A few travel agencies are using tapes as a sales tool, showing them free to prospective clients in the office or lending the films.

About a dozen travel video companies are now making one or more tapes. The technical quality is professional: full color, with good picture and sound. But in a sampling previewed recently, content and style varied considerably. Available primarily in VHS, the films generally run from 30 minutes to an hour. Prices range from around $19.95 to $39.95 each, and rental fees are about $2.50 a night, the same as those charged for full-length motion pictures.

Predictions about the future of travel videos are mixed:

"We've had lots of requests," says Mike Ackard, vice president of Travel Merchandise Mart in Washington, a bookstore operating as part of the Omega World Travel agency. The store sells a selection of travel tapes produced by two companies.

"I don't know how they will sell," says Elaine Tirella, assistant buyer for Waldenbooks. The chain has ordered five titles -- four of them on Europe -- as a marketing test for travel videos in its East Coast region, which includes Washington, Virginia, Maryland and Delaware. Tirella says recent concerns over terrorism may complicate the test because "people are reconsidering whether to travel overseas."

"These tapes have a limited value," says a European tourism official who agreed to comment on the condition he would not be identified. His country cooperated with video producers -- as have some other countries and airlines -- by loaning film footage from their library of travel scenes and helping pay for taping sessions. "Most agents have limited time and space to show them to clients," he says, adding that the films most likely to be marketable are those focusing on far-away and relatively unfamiliar places rather than major countries that receive strong exposure on TV and in the movies.

"The list of destinations is growing," says Christopher Gardiner, manager of Esprit Travel in Bethesda, which has 20 tapes on the Caribbean, Hawaii, Mexico, Europe and the Middle East that it shows to clients in a small viewing room. The agency also loans out tapes for free home viewing with a $25 deposit.

Some cruise lines have begun selling short videocassettes about cruising aboard their vessels to agents, who are using them to sell the cruises. Carnival Cruise Lines and Royal Viking Line say the tapes stimulate customer interest, and often passengers buy them for souvenirs.

Usually the videos follow a travelogue format, with a voice-over or on-screen personality presenting facts, guiding the viewer around the country or city, explaining what is being seen and occasionally introducing officials or other citizens during the journey. Though all are informative, they often differ in emphasis. One concentrates on tourism, while another may give a broad overview with cultural and documentary touches, and another focuses on accommodations with exterior and interior views.

All tapes avoid negatives and apparently seek to avoid being too specific so they will not be outdated too quickly. Unlike some major guidebooks, they generally are not being updated annually in order to limit production costs. Another way the travel video companies are reducing costs is by using existing film clips, which they get from government and state tourist offices, cruise lines and from independent film producers within various countries or cities. The companies pay cash or sign a royalty or licensing agreement, then assemble the segments and add their own footage and commentary.

Area stores where travel videos can now be purchased or rented, and examples of the products being handled, include:

*Waldenbooks. VHS tapes on London, Paris, Rome, Spain and Hawaii from the "Laura McKenzie Travel Tips" series are expected to be in stock early this month. Price, $24.95 each. Produced by Republic Pictures Home Videos, 12636 Beatrice St., P.O. Box 66930, Los Angeles, Calif. 90066-0930.

*Tower Records, 2000 Pennsylvania Ave. NW. Several titles in the "Journey to Adventure With Gunther Less" series, rental only, both VHS and Beta. Produced by A & H Video Sales Representatives Inc., 430 West 54th St., New York, N.Y. 10009.

*Safeway. One tape, "How to Visit Hawaii," produced and narrated by Jay Jarman of Burke, Va., is being sold ($39.95, VHS and Beta) and rented by those Safeways with video stores operated by Entertainment Now. Jay Jarman, Travel Video International, 5822 Banning Pl., Burke, Va. 22015.

*Travel Merchandise Mart, 1425 K St. NW. Jarman's Hawaii tape and several titles ($19.95 each, VHS) from MGF Videotravel Inc., 2113 North Charles St., Baltimore, Md. 21218.

*Travel Books Unlimited, 4931 Cordell Ave., Bethesda. Several MGF videos for sale.

Two of the largest video rental chains in the Washington metropolitan area, the 7-Eleven stores and Erol's, do not presently stock travel videos. A spokesman for Erol's said they are waiting to gauge the demand before deciding whether to handle the films. Meanwhile, some of the producers seeking distributors for their tapes will sell them by mail. Among them:

*Travel Video Corp., 3320 East Shea Blvd., Suite 175, Phoenix, Ariz. 85028, (800) 826-5557 for information, (800) 336-3737 for mail orders. Thirty-minute tapes include "Cayman Islands," "Old West Trail Country," "Ski Vermont" and "Florida Gulf Coast." The price by mail, through June, is $19.95, plus $4 postage and handling for the first tape and 50 cents for each additional video; the regular suggested retail price is $29.95.

*Van Arsdale's Video Travel Guides, 281 11th Ave. South, Naples, Fla. 33940, (813) 649-5828. The company's initial tape, "The Best of the Caribbean," covers 10 islands and more than 60 hotels and guest houses in about 80 minutes. Price: $24.95 plus $1 for postage.