For their size and the number of passengers they carry -- Royal Caribbean's gigantic Freedom of the Seas holds the current title, with capacity for 3,600, double occupancy -- cruise ships are surprisingly nimble. They have, after all, responded to recent consumer demand for flexible dining, a larger selection of cabins with balconies and more U.S. homeports with great enthusiasm. Dining rooms were added, entire ships retrofitted to add outdoor lounging space and itineraries rewritten to accommodate both weather events (Hurricane Katrina) and historic events, such as the opening this spring of the Brooklyn Cruise Terminal in Red Hook, Brooklyn (a former cargo pier).

But as the popularity of cruising grows, and vacations at sea attract an ever more diverse and often younger clientele, cruise lines are responding to new requests that expand and improve upon those earlier modifications. Here's a look at the trends shaping your next cruise, whether it's a five-day jaunt to the Mexican Riviera, a week in Alaska or the Caribbean, or one or more legs of an around-the-world cruise of a lifetime.

Although the Caribbean continues to hold top spot as a cruising destination, more and more ships are beginning to explore less traditional ports in this part of the world and elsewhere. The islands of the Grenadines, Trinidad, Tobago and Curacao offer sun-seekers the sugar-white sand beaches they crave, while ports like Willemstad and Pointe-a-Pitre give explorers and shoppers the chance to roam quaint streets and colorful, open-air markets. Traditional cruising routes in the Mediterranean are also expanding to include new ports of call. The Royal Princess, for one, will drop anchor in Ravenna, Italy and Split, Croatia next year, just two of four new European ports featured on Princess's 2007 calendar. Even Disney Cruise Line is getting into the act, repositioning its Disney Magic to Barcelona next summer for 10- and 11-night voyages to Rome, Pisa, Cannes and Florence. Other major cruise lines are making their first trips to the Holy Land in almost five years.

When it comes to keeping kids happy on a family cruise, one size definitely does not fit all. Family-oriented ships have diversified their children's programs to suit toddlers, school-age kids, tweens and teenagers. For the little ones, dedicated activity rooms and fully supervised wading pool areas mix the bright colors and nautical themes they love. Older children can choose more sophisticated pastimes, including arts and crafts, pottery, cooking and yoga classes, and tours of the ship. And much more attention is being paid to teenaged cruisers. On Holland America ships, for example, they now flock to The Loft, an open concept hang-out inspired by a New York artist's loft. There's music, videos, a karaoke system and laser lights for dance parties -- and it's open until midnight! Accessed by a special passageway from The Loft is The Oasis, a secluded, teens-only sundeck with hammocks, lounge chairs and a waterfall for cooling off. Other lines have incorporated video arcades, Internet cafes and soft-adventure shore excursions into their kids' and teens' programs. Carnival, acting on the (correct) assumption that parents sometimes like to join in the play too, also offers family activities such as water balloon tossing and cookie decorating.

Hot on the heels of land-based resort trends, cruise ship spas are expanding in size and services. Long favoured by Europeans, thalassotherapy is fast becoming a popular, pamper-yourself-at-sea option. On the QE2 and Celebrity's Millennium, among other ships, these body-temperature, salt-water pools relax muscles and soothe stiff joints. On the Seabourn Sun, you can try a dry-float table, which cradles you in the water without getting you wet. Several cruise lines (RCCL, Celebrity, Disney) now offer rasuls, tile-lined steam rooms where passengers apply their own mud-based treatments as a heavenly soundtrack filters into the darkened room and a "starry" ceiling twinkles above.

The public pool areas, too, are undergoing exciting renovations. Both Enchantment and Freedom of the Seas ships have replaced traditional swimming/hot tub areas with onboard water parks. H20 Zone is interactive, spouting cool jets of water from umbrellas, waterfalls, buckets and spray cannons. There are two pools, four whirlpools and 64 jets connected to a touch-pad system that turns the area into a wonderful fibre-optic light show at nighttime.

Themed cruises were considered innovative in the 1990s, appealing to fans of Big Band music, devotees of baseball, ardent gardeners, film noir buffs, serious ballroom dancers and others. And while there are still lots of those on offer, cruise lines are taking advantage of their bigger ships and more flexible meeting, eating and entertainment spaces to cater to passengers with very special interests. RCCL invites motorcycle owners to bring their bikes along for a Caribbean cruise, offloading riders and their Harleys, Hondas and BMWs for group or individual tours in the ports of call. Crossword puzzle addicts will get more than their fix sailing with puzzle guru Stanley Newman on next January's Holland America Oosterdam cruise from San Diego to the Mexican Riviera. For a real buzz, join the Coffee Cruise on the Norwegian Sun next March, featuring tours of coffee plantations in Mexico, Guatemala and Belize, not to mention a high-octane series of coffee tastings, retailer roundtables and workshops scheduled onboard.