7. Access to the Cloud 9 Spa Thermal Suite

We don't always love our massages and facials on spas run by Steiner, which handles the spas on Carnival ships — too much plugging of products for our taste. But the thermal suites are a calm, soothing place to spend a sea day — and they're easily the best place on board to relax on rainy days. Look for heated tiled lounge chairs, steam rooms scented with a variety of fragrances, and thalassotherapy pools. Note: Carnival Sunshine has a smaller, one-story spa without a thalassotherapy pool, and Carnival Vista has a whirlpool tub instead of a thalassotherapy pool. So if you're planning to spend a majority of your time on board in the spa, you might want to consider other ships.

Tip: On sea days, the spa can be packed, whereas you may have the place to yourself when the ship is in port.

Cost: $20 per guest per day on Carnival Sunshine; $40 per guest per day on all other ships. If you want to go more than one day, you'll save money with a pass that lasts the duration of your cruise.