Imagine the scene: A 25,000-ton, 900-passenger, nine-deck cruise ship towers over the homey, historic village of Old Town Alexandria. Virginians line the Potomac riverfront all the way down to Jones Point, waving streamers and calling out as the floating hotel pulls away from the dock. The passengers, most of them locals en route to Bermuda or the Bahamas, are racing from port to starboard, forward and aft, drinking in the waterfront views of Fort Washington and Mount Vernon as though they'd never seen them before.

Actually you don't have to imagine it at all. Next summer and fall, this very action returns to the humble port of Alexandria, thanks to Ed Didion, owner of Didion World Cruises, a District-based cruise-only travel agency. Didion has chartered Norwegian Cruise Lines' Leeward, a four-star cruise ship, for a season of cruises departing from a dock at the foot of Oronoco Street. Sailings begin July 27 and include Bermuda, Canada and the Caribbean.

Didion is solely responsible for putting Alexandria on the map of the world's leisure cruising ports. A cruise ship reservation agent turned agency founder, he chartered his first ship serving passengers from Alexandria in 1992. For five weeks and $2.5 million, Didion "owned" the Crown Monarch, for which he marketed cruises, sold berths, made cabin assignments, determined itineraries and arranged port departures and arrivals -- while relying on the established cruise line and its crew for on-board operation, service, food and entertainment. The next year he leased the Monarch for eight weeks, and in 1994 he hosted cruises on a cousin ship, the Crown Jewel.

The sailings were successful, attracting an obsessive cadre of area cruisers who'd long felt slighted by the industry. Major liners call in at ports at Hampton Roads, Va., Baltimore, Philadelphia and Boston, but not the Potomac shore. And most passengers wind up flying to Miami or Fort Lauderdale, the East Coast's highest-volume cruise departure ports.

But then came a three-year drought. According to Didion, there were no available ships to charter. Oh, sure, a handful of couples who met on an Alexandria-to-Bermuda sailing a few years back tried a traditional cruise with Holland America, and it was nice enough. Mike McNair, an Alexandria travel agent, worked hard to get others to catch a Celebrity Horizon out of Baltimore (whose Dundalk dock hosts eight or 10 ships per year). He approached 200 couples; only three booked. The general response: "It's not my town, not my cruise."

Now, Didion's back. Nabbing the MS Leeward -- a ship that has borne such distinguished travelers as George Herbert Walker Bush and Jimmy Buffett, and features spas and piano bars, discos and Broadway-style theaters, casinos, hot tubs, formal and casual eateries, basketball courts and a swimming pool -- is a coup, despite the more than $6 million Didion must pay up front. It's safe to say that local cruisers have never seen a grander ship depart from such a convenient port.

But lest one think that the toughest part of Didion's job is selling berths, there are other daunting challenges. There are some very good reasons why no major cruise line has ever attempted to bring a modern floating resort up the Potomac. Only five or six recent ships in all of cruisedom are physically capable of sailing our way, because the Potomac River can accommodate a ship with a maximum draft -- that is, the part of the vessel that's underwater -- of 19 feet. The Leeward's draft makes it just under the wire at 18.5 feet. Most cruise ships have drafts ranging from 23 to 26 feet. (Large military craft, with drafts in the 30- to 40-foot range, can't navigate the Potomac, although smaller military craft do sometimes dock at Alexandria. Alexandria's limited cargo business is handled mostly at Robinson Terminal, a newsprint-handling facility owned by The Washington Post Co. Didion's cruise ships will dock at Robinson.)

The Potomac owes its relative shallow level to an environmental question being debated by the Army Corps of Engineers, which has plans to dredge to 24 feet, once it determines where "to locate suitable placement for dredge material," according to spokesman Doug Garmen.

Once Didion's ship pulls away from the pier, there's another challenge: getting past the Woodrow Wilson Bridge. Although it takes only eight minutes for a cruise ship to clear the bridge, the opening creates a three- to five-mile backup on the Beltway in both directions. Ships are restricted from passing between 5 and 10 a.m. and 3 to 8 p.m. on weekdays, and from 2 to 7 p.m. weekends. But even with these restrictions, the crew can handle a typical cruise turnaround fairly easily. If the ship docks in Alexandria before 5 a.m., the crew has until shortly before 2 p.m. to disembark passengers and luggage, clean, restock, refuel and board another set of 900 passengers. It's tight but doable, Didion says.

The 10 to 15 hours it takes to sail from Alexandria to the Atlantic -- a length similar, by the way, to that traveled by a ship embarking from Baltimore's Dundalk cruise ship port -- isn't a problem, though it does limit Didion's itineraries to ports that are closer by.

But even the most hardened Washingtonians -- and most veteran cruisers -- are thrilled to see familiar riverscapes viewed from atop a cruise ship. A submarine sighting one summer morning was quickly dubbed the "Washington equivalent of whale watching." Actually, the real difficulty is that the Potomac, with its bends and twists and varying depths, is a challenge to navigate. Particularly when the vessel in question is a cruise ship.

"Let's say you normally drive a Volkswagen when suddenly you're driving a Chevy Suburban through the streets of Washington," says Rick Amory of the Virginia Pilots Association, whose members are responsible for piloting cruise ships from Cape Henry, at the mouth of the Potomac, into Alexandria. "It's much more car, much more awkward. If you had to parallel park, it could be nerve-racking. It's a task that requires every bit of attention. But in the end it's a job, like every other job."

If you ask any of the more than 12,000 past Didion passengers, many of them experienced world travelers, why they choose his ships, the common answer is the huge appeal of convenience. The journey between home and dock and back is the most reviled part of any cruise. One of the paradoxes of cruising is that you spend days being pampered and coddled and then you're spit back into the real world of missed flights and broken-down buses.

Too, there is also a certain hometown coziness that derives from traveling on a relatively intimate ship, in which more than half the passengers hail from the same town. There's a sense of, well, civic pride on these cruises. "For locals, this has become `their' ship," McNair says.

Details: Cruising Alexandria

Didion Worldwide Cruises has chartered Norwegian Cruise Lines' Leeward for next summer and fall, and is marketing a variety of sailings from July 27 through Sept. 27.

The first is an eight-night positioning cruise, which begins in Cancun and winds up in Alexandria. There are two week-long cruises to Bermuda. Two northbound Canadian cruises are available, which depart from Alexandria and arrive in Mon-treal. There are an additional two heading southbound from Canada via Quebec City and Bar Harbor, Maine, before arriving in Alexandria (the north and southbound can be combined for one two-week cruise). There's also a three-night-to-nowhere jaunt, perfect for first-timers and, as Didion describes it, a "party boat." A six-night repositioning cruise heads from Alexandria to the Bahamas to complete the season.

Chartering well-known cruise ships is fairly common. Apple Vacations, for example, has long been leasing Celebrity Cruise ships for Bermuda sailings from Philadelphia and Baltimore. In Didion's case, all on-ship operations -- from piloting the cruiser to housekeeping, food service, entertainment and on-shore excursions -- are handled by Norwegian's regular Leeward crew.

Didion offers two sets of rates. The best discounts are the 90-day advance purchase. Prices are comparable with similar sailings from New York. For example, from Alexandria, a six-night Bermuda cruise with outside cabin costs $1,100.50 per person, double occupancy, including port charges. The per day cost: $183.42. If you go with NCL itself out of New York on the Norwegian Crown, also with outside cabin, you'll pay $1,339.50 per person, double occupancy, including port charges for the seven-night trip ($191.36 per diem). Plus, you get a "free" 5 1/2-hour bus ride to the New York pier!

For information or reservations, call a travel agent or Didion World Cruises at 703-299-3490 or 1-800-524-6258.