Next time you take a cruise, be sure to stuff your wallet with extra bucks. For decades, cruise lines pumped up the public with the notion that cruising is the all-inclusive vacation. And most cruisers - particularly first-timers - still expect that. But many lines, if not most, have been changing the rules of the game.

The seagoing vacation that used to be all-inclusive seems to be drifting toward a la carte, with passengers paying unexpected shipboard expenses. This gradual migration to add-ons may well be shaping up as a trend.Passengers always have paid extra for alcoholic beverages, spa services, shore excursions and shipboard shopping. But many of the newest inducements that lure you aboard in the first place - particularly those offered by mainstream cruise lines - carry a price tag.

For example, most lines levy a cover charge - a thinly veiled tip - in their alternative restaurants. Princess Cruises charges $3.50 per person in Grand Princess' Italian and southwestern eateries, and Disney Cruise Line will levy $5 in Magic's adult restaurant when the ship begins cruising Thursday. Crystal Cruises charges $5 on Symphony and Harmony in alternative dining areas, and Norwegian Cruise Line, perhaps the first to offer alternative dining (in the late 1980s), suggests tipping $5 in its bistros.

But wait, there's more. Want a cup of cappuccino on Royal Caribbean International? You'll pay $1.50 for it. Care for some cheesecake in Carnival Cruise Lines' specialty cafe/patisseries? Fork over $2. A sundae at Princess' Lido Deck ice-cream stands costs $3.75 because, says the line, it's Haagen-Dazs, a premium brand.

Whiz-bang virtual-reality games and rides on ships of Carnival and Princess cost from 50 cents to $3 to play. And on Princess ships, you must buy a $20 game card to indulge at all.

And when Holland America recently announced it would hold continuing education seminars developed in conjunction with Eckerd College in St. Petersburg, Fla., it also noted that courses cost from $69 to $199 to audit.

When she heard the news, Anne Campbell, editor of America Online's Cruise Critic, commented, "What? Are we now paying for lectures?"

So even though cruisers get more on ships these days, they're often paying extra for it. Industry watchers say the reason is twofold: Stiff competition to discount fares forces cruise lines to look for revenue, and ever-bigger ships - with ever more options to woo you - cost millions to build.

Says Kay Showker, cruise expert and author of "The Unofficial Guide to Cruises" (Macmillan): "Cruise lines not only milk every profit center, now they're even looking for new ones."

Tim Gallagher, Carnival's vice president of public relations, disagrees.

"Those optional items available for purchase on board are there as a convenience to our guests, not as a revenue generator," he said, adding that a la carte items are not being used to fund cruise discounts.

Nevertheless, many cruisers are surprised about what one ticked-off passenger dubbed "getting bucked." Cynics of the trend ponder the future.

"Where would you draw the line? Should they charge you . . . for dinner? How about a fee for letting you use the tenders?" asked a veteran cruiser in a message posted on an online cruise bulletin board.

Cruise lines note that they're building ships with more choices. Says Gallagher: "As the industry has moved to position itself as an alternative to resort vacations, the cruise companies have tried to offer greater choice to their guests. Not all of these can be done with no charge."

Of course, most things aren't free in the real world. But "this nickel and dime stuff is starting to cheapen cruising," said another disgruntled cruiser on the online message board. It's the principal, passengers say, not the money per se; the nuisance of bumping into a price tag at every turn is offputting.

It's not so nickel and dime, either. Paying $3.40 (including a 15 percent mandatory tip) per 1.5-liter bottle of water seemed excessive to many Grand passengers on a recent cruise. And the issue of ice-cream charges came darn close to meltdown.

Francois Morin, a recent Grand passenger, was angry that ice cream and Coke aboard the ship weren't free "when you pay thousands for a cruise."

Princess' Brian Langston-Carter defended the ice cream fee as a means of keeping passengers from hogging the Haagen-Dazs.

"I'll tell you what," he suggested hypothetically, "I'll open the ice cream bar for free tomorrow, and you'll see 3,000 people lined up."

Try us.

On some ships, what you're expected to pay for is not always clear - until it's too late. For instance, you're likely to tipple from that tray of soft drinks that greets you in your cabin on Royal Caribbean ships before you notice the price list tucked behind it.

Some things are free in some places but not in others. Take orange juice, for example. On most mainstream ships, it's free from, say, room service, but it'll set you back about $2 if you ask for it at any bar. And if it's not "the juice of the night" on Celebrity Cruises ships, you're charged $1.50 for it in the dining room.

Ultimately, I see the a la carte trend as much sociological as economic, and wonder if it doesn't herald a subtle shift backward to two-class cruising. Remember Leonardo DiCaprio on "Titanic"? When less-well-off passengers have to forgo pleasures that well-heeled passengers can blithely indulge in, I think the issue of choice - the latest buzzword of cruise lines - takes on a somewhat less-democratic inflection. It becomes not so much a matter of "do I want it?" (you probably do) but more like "do I want to pay extra for it?" Cruises didn't used to be like that.

Meanwhile, cruise lines plunk lots of advertising dollars into selling you a dream. While their ships sure do deliver, maybe dreams just no longer come free.