In its defense, this tactic is not limited to Norwegian or even to cruise lines. Hotels have been quietly slipping a ''service charge'' into bills for years so companies can collect more of your money without raising the advertised price -- and with no guarantee that any of it actually goes to the workers who provide the service.

Each cruise line deals with tipping differently. Beware: In most cases, the ''per passenger'' applies to all ages, even infants. (Note: Almost all lines now add a 15 percent gratuity to bar bills, although I've met plenty of bartenders who swear they've never seen a dime of that.)

Here's a brief summary of the basics among the major lines that serve North America:

• Carnival and Holland America: $10 per day per passenger; adjustable through the purser's office.

• Costa Cruises: $8.50/day in the Caribbean, 6 euros/day (about $8.88 US) in Europe; grudgingly adjustable.

• Cunard: $11/day; adjustable.

• Disney: Offers guidelines (about $11/day) but leaves it up to passengers. Gratuities can be charged to your onboard account.

• MSC Cruises: $12/day; adjustable.

• Princess: $10.50/day; adjustable.

• Royal Caribbean and Celebrity: Both offer traditional tipping guidelines (about $10.50/day) and envelopes, but leave it up to passengers. Gratuities can be charged to your onboard account.

If they can charge extra for basic service, what else might you be charged for in the future? Here are a few comparable (albeit unlikely) new charges:

Seaworthiness Surcharge: A $3-per-day fee that supplements the watertight properties of the hull. Adjustable in the event the ship sinks.

Porcine Reconciliation Fee: A $2.50-per-day charge based on the likelihood that passengers will eat fried pork products at the buffet. Pooled money pays for new treadmills in the gym.

Land-based Mooring Tax: A vague extra fee that passengers pay for the ship to stop at a port.

Oops. Turns out that last one already exists.