468 Discover More- Dive Dolphin! More Dolphin Facts WATCH NOW! Other National Geographic Books Explore more of the books within this series! National Geographic Readers: Sea Turtles National Geographic Readers: Coral Reefs National Geographic: Ocean Play Sand Fresh River Dolphins WATCH NOW Learn about Dorsal Fins! There are 12 different types of dorsal fins! Have an adult help you read about these fins or watch the video at the bottom of the webpage!