My mom stayed on the ship and my son and I got off and explored the town. We just shopped, ate ice cream cones and went on the glass bottom boat. As I have dived there, it wasn't real exciting for me, but a good option for those with children or people who can't snorkel or dive. They also have a submarine tour that will really excited small children, but it is really just a glass bottom boat with the windows on the side. It doesn't dive. For the price the glass bottom boat is a better deal.
Also it was half the price booking it off the ship than through Carnival. I would not book any Catalina excursion through Carnival and they are all available for sale on the dock for a much better price.
I enjoy going down to the fish market area and eating fish tacos. Yummy, better than anything I had on the ship.