Carnivale Valor in May!!
I wasn't on the Valor, but I have been to Belize and Grand Cayman. Last summer in Belize we did this: http://carnival.com/ShoreExcursionDetails.aspx?portcode=BZE&excursionname=Altun+Ha+Mayan+Site+%26+River+Wallace&excursioncode=509002
In Grand Cayman a few years ago, we snorkeled with the Sting Rays. There are several groups that offer this. It has to be one of the most exciting things I have ever done. IF you want more information, or pics, please feel free to email me.
Judy