I think the commercial may have been misleading. For aqua class, access to the spa is included but only for use of the common rooms such as the sauna, and thermal loungers. Spa treatments are not included. As mentioned earlier, they are pricey. Very pricey. If you are choosing the vacation based on that I believe you will be disappointed as you will need to tack on hundreds of dollars per day for treatments.
What you will have access to is the fitness classes, in-room exercise equipment (yoga mats, weights, etc). You will also have access to Blu which is suppose to provide a healthier fare than other dining rooms but looking at the menu is not terribly so.
If you want a cruise with some spa like amenities, then try it out. If you are looking for a true wellness retreat type experience I think you will be disappointed.