Since Fernandina lies to to the very west of the Galapagos archipelago it has no introduced species, and as a consequence remains as the Galapagos were before being colonized.
La Cumbre (the summit, about 1500m) is a highly active volcano with a large caldera and surrounded by several smaller craters. Most of the island is covered in lava flows, so there is not much vegetation.
The island is surrounded by shallow rocky reefs that are covered in the green algae that is the only diet of the marine iguana. Fernandina geological information - Fernandina (Global Volcanism Program)
There are two dive sites, Punta Espinoza, located in the northeastern point of Fernandina island at the Bolivar channel between Isabela and Fernandina and Cape Douglas which lies further west. The water here is cold all the time, since Fernandina lies smack in the zone of major upwellings from the Cromwell submarine current.
