This is easy to unlock in
Episode 1: The Phantom Menace - A Bigger Fish. Here are the challenges:
Dis is Nutsen: Dodge 3 of the Opee Sea Killer's attacks in a row.
Dodge Every-fin: Defeat the Opee Sea Killer without taking damage.
Colo Snore Fish: Dodge 3 of the Colo Claw Fish's attacks in a row.
The attacks the fish make are slow and easy to telegraph. Simply it
or
when you see the button prompt. You don't even need to time it perfectly (slow motion dodge), though I did do that once while going for the challenges.