The laid-back beach of Playa Palancar is considered one of Cozumel's most beautiful, with fine white sand and access to an outstanding coral reef. Playa Palancar doesn't have the party atmosphere, or range of hotels and other services, boasted by some of the beaches closer to San Miguel, but for family-friendly fun and fantastic views, it's hard to do better on the island.
There are several small restaurants and shops selling seafood, drinks, and souvenirs, as well as renting snorkeling equipment and organizing dives.
Close to the beach turnoff, you'll see signs for El Cedral Mayan Ruins. The tiny cement house probably has some historic significance, but fails to impress most visitors.
While pretty Playa Palancar is surrounded by posh all-inclusives, it is a public beach. There's no public bus service (yet, but ask around in San Miguel to see if this has changed), but it is well signed from Avenida Melgar; look for signs before the Costera Sur exits inland. If you hire a taxi instead of a rental car, be aware that you may need to wait for a ride back to your hotel.
There are several restaurants on the beach, though few provide beach chairs or shade; come prepared. Boats wait to take snorkelers out to the famous reef, and you can rent equipment close by.