Octavius Rex is a giant red octopus who found a crown in a sunken ship's submerged treasure chest. Because of this, he claims to be ruler of the high seas, although he isn't even ruler of Cerulean Reef.
Octavius is also one of the game bosses for Force Field.
To find Octavius Rex, you must wear the diving helmet and click on the sign for Cerulean Reef found on Breakwater Beach.
Octavius Rex is also the name of a fish in the SpongeBob episode, / The Chaperone