Norwegian Gem
Line: Norwegian Cruise Line
Passengers: 2,376
Itineraries: Bahamas, Caribbean, Europe
The entire Norwegian fleet features Mandara-branded spas, known for their streamlined Asian look and top-notch therapies, and the year-old Gem has the Yin & Yang Spa, one of the fleet's largest, with 18 treatment rooms. The focus here is on thermal treatments: There's a hydrotherapy pool, tropical-style showers, aromatic steam rooms, and a sauna. Given the low prices on this ship's itineraries, the well-thought-out details—from oversize treatment rooms to heated poolside lounge chairs—are all the more impressive. Less appreciated is the one-hour limit on relaxing in the post-treatment rooms (to ensure that all passengers get in their relaxation time); for an extra fix, head to the complimentary steam rooms near the Body Waves gym. The Gem is also a haven for activity addicts, with a packed daily schedule of everything from rock climbing to bowling to Nintendo Wii on a two-deck-high screen (866-234-0292; ncl.com; seven-day Western Mediterranean trip from $679).

Queen Victoria
Line: Cunard
Passengers: 2,000
Itineraries: Worldwide
Even the most jaded spa goers were impressed when Cunard opened the first shipboard Canyon Ranch-branded spa on its Queen Mary 2. On the Victoria, an elegant new ship with wood paneling and Art Deco accents and lighting, Cunard continues to raise the bar with a 13,000- square-foot bilevel oasis with a polished, wide-ranging treatment menu. Your decompression begins the moment you arrive in the unfussy relaxation room, a flower-filled space with a Gustav Klimt print and views of the sea through a giant plateglass window. In addition to therapies using Comfort Zone products, there is a range of O2 Star treatments, which use high-tech oxygen-delivery systems to mimic the effects of plastic surgery, and Ayurvedic rituals. In keeping with the liner's bespoke feel, the special men's treatment menu includes an old-fashioned shave using traditional hot towels and straight razors. We also love the roster of fitness options, which range from the deliciously old-school fencing to the au courant Yo'Fit, a modern-day hybrid of yoga and Pilates. Even if you don't splurge on a treatment or a fitness class, be sure to purchase a $35 day pass for the hydrotherapy pool and thermal suite; the latter has three steam and sauna rooms, five heated thermal beds with ocean views, and is never busy (800-728-6273; cunard.com; 12-day Jewels of the Mediterranean trip from $2,995).