Before creating the American TV show "SpongeBob SquarePants", what was Stephen Hillenburg's occupation?

"SpongeBob SquarePants" is an American animated television series created by marine biologist and animator Stephen Hillenburg for Nickelodeon. The series chronicles the adventures and endeavors of the title character and his various friends in the fictional underwater city of Bikini Bottom.

Born in Lawton, Oklahoma and raised in Anaheim, California, Hillenburg became fascinated with the ocean as a child and also developed an interest in art. He started his professional career in 1984, instructing marine biology, at the Orange County Marine Institute, where he wrote "The Intertidal Zone", an informative comic book about tide-pool animals, which he used to educate his students. In 1989, two years after leaving teaching, Hillenburg enrolled at the California Institute of the Arts to pursue a career in animation.

As he was developing the show's concept, Hillenburg remembered his teaching experience at the Orange County Marine Institute and how mesmerized children were by tide-pool animals, including crabs, octopuses, starfish, and sponges. It came to him that the series should take place underwater, with a focus on those creatures: "I wanted to create a small town underwater where the characters were more like us than like fish. They have fire. They take walks. They drive. They have pets and holidays." It suited what Hillenburg liked for a show, "something that was fantastic but believable."