Hi Aegis.I took the Belize,Cozumel cruise on the IOS over Thanksgiving and I did the zip line and innertube ride in the caves.I really enjoyed the zipline and they take neat photos of you on it that you can purchase when your done.It was definitely worth doing and it's pretty easy plus you have neat photos to take home with you.The innertube ride was fun too.Have a great time on your cruise and enjoy.
Wayne