Belize - Cave Tubing was a blast if you are in decent physical shape. Your adventure begins with a 40 minute walk thourgh the jungle carrying your innertube. They provide life jackets if you would like to wear one in the water.
Cozumel - Horse back riding was really fun, the ranch we went to (not sure the of name but it was a tour though carnival) was beautiful the horses were well trained.
Progresso - under-developed area would suggest an excusion if you plan on getting off the ship. SInce this a new port there is no dock yet. We went kayaking (spelling?) would not recommend. The water was brown and smelled horrible.
Enjoy your cruise!!!!!!!