I know what you mean, it seems like FOREVER for your cruise to get there and then in a blink of the eye, it's over. However, planning and anticipation are fun, too! The last time we went to Antigua we negotiated with a driver, outside of the terminal. He took us all over the island, then to a nice beach with a bar/restaurant. It was a wonderful day and he only charged us $25/pp. He even stopped to help a stranded bus, which was fun. He told us that he was the island's mechanic and they all would come to him for help.
I don't know of any island I don't like in the Caribbean. San Juan is so much fun! Next time I'm in Antigua, I'll try your snorkel/kayak excursion. That sounds right up my alley. I love to snorkel. The first time in Antigua we did a snorkel and you couldn't swim for all the jellyfish. Might have been the wrong time of the year, I don't know. It was in October.