Belize is, for good reason, showing up on a lot of tourism websites. While Cayo isn't the main focus of this article(as it should be), it's still mentioned.
"A Central American country with amazing beaches and gorgeous waters that isn't Costa Rica... Jump on an inner tube and explore the limestone caves at the Nohoch Che’en Caves Branch Archaeological Reserve. This network of caverns was once the sight of sacred Mayan rituals. Cave tubing in Belize is a must when visiting mainland Belize."