A small, populated key near the jaws of the bay, Cayo Granma is a little fantasy island of red-roofed wooden houses – many of them on stilts above the water – that guard a traditional fishing community. You can hike up to the small whitewashed Iglesia de San Rafael at the key's highest point, or walk around the whole island in 15 minutes.
The best thing about this place, however, is just hanging out and soaking up a bit of the real Cuba. Eat at seafood haven Restaurante El Cayo or the clapboard Palmares restaurant jutting out over the water on the Cayo's far side.
To get to the key, take the regular ferry (leaving every one to 1½ hours) from Punta Gorda just below El Morro fort. The boat stops en route at La Socapa (actually still the mainland; the western jaw of the Bahia de Santiago) where there are decent beaches for swimming.