What do you do when you go to a new city for a day? Do you take a tour or explore on your own? I understand why one would want to use a cruise ship tour when you're travelling far from the ship, but for nearby tours, I suggest TripAdvisor for guidance, or google. There's a lot of scare tactics employed by cruiselines to get your to book through them, but if you plan to return to the ship 2 hours or more before departure, you'll likely be fine unless you fall off a cliff or into a ravine.