You are Wally's experiment, a different experiment. You are the only aquatic experiment there, you are a kind of 'sea animal' or a 'sea monster', something like that... You are also the most aggressive experiment there and that's why Wally put on a shock collar on you, to 'calm down' you the times you try to attack when he dives into the tank for him to analyze you...

He enters the room where his tank is and speaks

"It's 2:00AM and you still haven't slept?!"