10km (6 1/4 miles) S of Isla Colón

Isla Cristóbal is a 37-sq.-km (14-sq.-mile), mostly deforested island south of Isla Colón. The island and a peninsula that juts from the mainland form a nearly enclosed bay called Laguna Bocatorito, or Dolphin Bay -- so-called for the bottlenose dolphin breeding site found here. It is one of the region's most enjoyable attractions because dolphins swim up close to visiting boats and prance about. The best time to come is from June to September, when dozens of dolphins meet in the bay to create a wild version of Sea World. For the rest of the year, here's a tip: Try to visit the bay after the morning tour boats do their thing (which amounts to disturbing the dolphins by speeding around in circles in an effort to stir things up and draw the dolphins to the surface), and find a tour or book a custom trip going at a quieter pace. More dolphins show themselves when the bay isn't being churned up. Or better yet, arrange to head out on a kayak rented from the island's only lodge, Hacienda del Toro, which can even provide you with hydrophones to hear what's going on underwater.