This 3 sentence summary provides the key details about the whale shark encounter and overview of the Baja California trip:
The narrator has a close encounter with a whale shark in the Sea of Cortes near La Paz, Mexico, observing the giant fish up close while snorkeling without touching it per the guide's instructions. The summary then shifts to introduce that the trip involves exploring different areas of the Baja California peninsula over the course of a week, including the Sea of Cortes side, Pacific side, and rugged desert interior. Overall the document sets up an experience with whale sharks in Baja California and previews the varied locales to be visited on the peninsula.