Puerto Villamil is an idyllic spot for whiling away a few days in the Galapagos, if you choose to not do a cruise. A local guide will take you along the coast here, to see thousands of migratory birds and their nests.
Then a speedboat will take you out to the Teinoreras islets, where a walking trail reveals marine iguanas and sea lions. From the boat you can watch sharks swarming in narrow underwater crevices. Elsewhere there are penguins and pelicans, along with the looming cone of Sierra Negra.
With one or more days you can combine land-based wildlife safari with snorkeling and scuba diving. Isabela has seven underwater sites and these provide a beautiful mix of big fish, sea lions and diving cormorants.