Conversation so far:
What did Stephen Hillenburg start his career in?
Teaching
What subject did Stephen Hillenburg teach when he became a teacher?
Marine science and maritime history.
Did Stephen Hillenburg teach any other subjects in his early career besides marine science and maritime history?
He taught tide-pool ecology, nautical history, diversity and adaptation.
In his early career, did Stephen Hillenburg come up with Sponge Bob
Some evidence shows that the idea for SpongeBob SquarePants dates back to 1986

Question: What year was he teaching or start?
Self-contained rewrite: What year did Stephen Hillenburg start teaching?