Hello Sheila B,
I usually visit the spa and take the free classes on every cruise I have been on and they are usually fun, and you get to meet other people who often have things in common with you such as...
wanting to get some exercise between all those meals
I have also taken some of the 12.00 classes and found that they are enjoyable as well and actually cheaper than at some gyms. So, hope you try them and have fun!