Cas Abao is a broad white-sand beach on a sheltered bay, with clear water and shade from palms and palapas. The rocky edges are the best places to snorkel, while a dive shop provides access to the reef farther out.
This is a managed beach rather than a remote cove: there is an entrance charge, and you will find loungers, showers, a bar, and food on site. That makes Cas Abao an easy choice for a full beach day, though arriving early gives you more choice of shade.