Dougherty's seminar cost $30. A nutrition book was another $30. As the minutes ticked by, so did the sales pitches, until the 37-year-old communications consultant found himself debating the merits of a $15 brush to shed weighty skin cells. Calling it "absurd," he declined.

"Cruise ships fatten you up for free," Dougherty says. "For a charge, they'll teach you how to lose the weight."

Cruise lines have always charged additional fees for onshore excursions, alcoholic beverages, and spa treatments. Now, lines are expanding their menu of extras to include luxuries such as premium restaurants and rock-climbing walls.

"It's not a new charge for an old thing," says Wayne McCaulley, president of Cruise Holidays in Bellevue, Wash. "It's a new charge for new, upgraded experiences."

Why the proliferation of pricey amenities? Cruise lines are struggling to wring extra dollars from an industry adrift in the economic horse latitudes. After last year's terrorist attacks, bookings sank 50 percent as travelers stuck to terra firma. Though reservations are rising again, cruise lines face another problem: A building boom is flooding the industry with ships. Thirty-two will arrive in the next three years, says Mike Driscoll, editor of the industry newsletter Cruise Week. The Cruise Lines International Association expects 63,468 more berths by 2006. The consumer benefit is lower ticket prices. In May 2001, a seven-day Caribbean package for two with an outside cabin on Carnival's Triumph cost $3,111. This May—$2,494. But buyer, beware: Inexpensive cruises quickly become very costly if you overindulge in extras.

On Disney Cruise Line, tickets to a floating film festival with critics Roger Ebert and Richard Roeper start at $534. Carnival Cruise Lines charges $25 for a dinner at David's, its steak house on the Pride. Princess charges $3.75 for a Häagen-Dazs sundae in its premium ice cream parlors. Passengers with Royal Caribbean can pay $230 for a two-hour seaweed-and-sage body wrap.

It adds up. A California couple, Charles Burrows and Minnie Yeh, applauded the magician who conjured their martinis on a seven-day Carnival cruise to the Mexican Riviera, but not the $485 bar tab they paid when they disembarked in Los Angeles.

"I don't know how you can avoid extras," Burrows says. "They keep telling you, 'You earned this! Indulge yourself! Drink!' They're conditioning you to party."

But most ships make clear what costs extra. "Princess never captured a penny of ours involuntarily," says Victoria Dougherty. "Any extra expense we incurred was for our pleasure. Being decadent San Franciscans, we bought Häagen-Dazs and drinks every night."