The Intertidal Zone is an unpublished educational comic book written and illustrated by Stephen Hillenburg in 1984. He created it to teach his students about tide pool animals while he was working as a teacher at the Ocean Institute. The book and its sea creature characters were instrumental to Hillenburg's later creation of SpongeBob SquarePants.
Stephen Hillenburg made The Intertidal Zone in the mid-1980s to teach children about different sea creatures. He worked as a marine science educator at the Ocean Institute in Dana Point, California. While working on Rocko's Modern Life, Martin Olson found pages from the book and liked them. He suggested that Hillenburg develop The Intertidal Zone into an animated series, which became SpongeBoy Ahoy! (later retitled SpongeBob SquarePants).
Hillenburg was interviewed about the book for SpongeBob Comics No. 1. He said, "I drew it while teaching at what is now called the Ocean Institute, to help explain the life of organisms living in tide pools along the Southern California coast in an entertaining way." He named Robert Crumb and Paul Driessen as influences on the visual style of the comics.
The book was co-hosted by two sea creatures: a shrimp named Rocky and Bob the Sponge, a very early version of SpongeBob. Each issue featured ocean facts and illustrations of tide pool creatures. Starfish, snails, scallops, and anemones were some of the sea creatures that appeared.
- The Intertidal Zone is mentioned in the "General Trivia" for SpongeBob SquarePants on Amazon Video. It mistakenly states that Hillenburg drew The Intertidal Zone in college; he actually illustrated the book while teaching at the Ocean Institute.