Crystal Cruises is a new cruise line with a new ship, the upscale Crystal Harmony. It recently made its debut. Here are some facts about the ship:

- Builder: Mitsubishi Heavy Industries, Nagasaki Shipyard, Japan.

- First cruise: July 24, 1990.

- Champagne-breaker (the ship's godmother, in other words): Actress Mary Tyler Moore.

- Vital statistics: 791 feet long; 97 feet wide; 49,400 gross registered tons (the standard measurement of a ship's size).

- Power plant: Propelled by two electric motors powered by four medium-speed diesel generator engines and one auxiliary generator engine. It's so smooth that, at times, you aren't sure you're moving at all (stormy seas notwithstanding). Only when it goes backward - - leaving a pier, for instance - does it shudder noticeably.

- Capacity: 960 passengers; crew of 505.

- Cabin size: The least expensive stateroom measures 183 square feet, with two single beds, sofa, desk and full bath. The costliest has 948 square feet, with separate areas for bedroom, dining room and sitting room, and it includes a long veranda. A midprice cabin has 246 square feet, including a veranda.

- Tidbits: Cabins have all the essentials: 14- channel TV and radio with CNN capability; built-in VCRs (the library has a stock of tapes to loan); movies and documentaries; minirefrigerators (bring your own goodies if you wish, or stock up at a port for private parties); and a pair of thick, white bathrobes, not to be taken home.

- Movies: The 270- seat Hollywood Theatre features recent films on a bigger screen than your neighborhood multiplex ("Driving Miss Daisy," "My Left Foot," "Glory" and "Born on the Fourth of July" were showing in July).

- Extras: Business offices with fax machines and word processors; self-serve washing machines (with free soap) and dryers; free safes, operated with dial-yourself electronic codes, in the closets; and four handicapped-fitted cabins.

- Advice: If you plan to be a Crystal Harmony guest, pack lots of elegant party clothes and formalwear, swimsuits for the Jacuzzis and pools, and casual-smart informal wear for daytime and shore excursions. But leave your steamer trunks at home; closet and drawer space is adequate, but not vast, at least in standard cabins. Likewise for bathrooms in standard rooms: All have tubs and showers, but it's a tight squeeze. If you pay top dollar, you can relax in a huge whirlpool on your private deck.