Crystal Cruises has launched what it says is the "richest" friend referral program in the cruise industry.

Convince a friend who has never cruised with the luxury line before to book a cabin and you get a shipboard spending credit of $250 to $400.

Bring along four friends and get four times that. A couple sharing a stateroom and bringing four friends each would get up to $3,200 (four being the maximum for the offer).

The shipboard credit can be used for onboard spending, including wine and drinks and shore excursions.

The "Bonus Share the Experience" offer applies to nearly any Crystal sailing between September and April.

The $250 credit is for Mexican Riviera cruises, while the $400 credit is for other cruises. The line operates two ships, the 922-passenger Crystal Symphony and 1,070-passenger Crystal Serenity.

The catch is you and your friends have to sail on the same cruise in a separate stateroom.

The new guests will receive a bonus too - $100 to $200 in shipboard credit per stateroom.

The credits are larger than the line's existing programs and you don't have to be a past guest to take advantage of the offer.

"Travelers won't find a richer referral program in the industry. The "Bonus Share the Experience" program affords the biggest incentive - as much as four times the standard shipboard credit amount for referrals - on more sailings than ever," says Bill Smith, senior vice president, sales and marketing.

Smith adds the cruise line views its guests as its "most valuable ambassadors."

But the line has also gotten very good press of late. Both the August 2010 issues of Travel + Leisure and Condé Nast Traveler magazines tout the Crystal ships in best in the world categories.

Sailings included in the new promotion are in the Mediterranean, Caribbean, New England/Canada, Mexican Riviera, South America, Panama Canal, Trans-Atlantic, December holiday cruises (including Hawaii) and the 2011 World Cruise. The offer can be combined with other Crystal promotions.

Photo courtesy of Crystal Cruises