It will also appear when you finish playing with one of the characters once. Only its silhouette will appear, the character will make a '?' on its head and swim away after it. Characters that make the '?' are: Boris, Layla, Edie, Peter and Harry,
He appears 10 times in total, or 1/6th of the game, first in Showdown in the Shallows and last in Monsterrific.
How to kill him:Edit
When you see him first, you must bite the red circle, much like to the barracuda. After being bitten, he will try to eat you and like the barracuda, he will let you after some time.
ALWAYS, when you must fight him, there will be mines. Just lead him to a mine. He will be stunned and 5 Shrinkshrooms Bubbles will appear. Each eaten Bubble will decrease Intruder's health. When you fill the bar in yellow, it will get small and the character will swim after him, with the exception of Eddie, which doesn't fight him and Boris, which will eat him.
When playing as Peter, you can just have the chance to eat Shrinkshrooms when a pelican is nearby, making it small and eatable.
When a Shrinkshroom is eaten, it will turn red, which could indicate some sort of upsetness or abuse.
When you first defeat him, he will be truly huge, then smaller and smaller.
He will not inhale in The Spoiler and not for the first half of Pull the Trigger, the only female character boss battle. He utilizes all zones but the Buccaneer Bay and could have possibly summoned the leopard sharks. The Sharktooth Ridge is the only zone in which he is fought twice. He looks like a cross between Edie and Orville the Orca from the first Feeding Frenzy and compared to the Shark King, is higher on the food chain than him. His antenna may also indicate that he has lost night vision before invading, but making it practically useless.