Here is the full list of all 22 Plunge achievements.
Defeat 500 enemies
Unlock Nox
Clear the Ironblocks
Unlock Bellow
Unlock boy Billie
Escape with Mortar
Escape with girl Billie
Escape with boy Billie
Escape with Bellow
Escape with Nox
Escape with Chant
Escape with Crook
Escape with Warden
Unlock Chant
Unlock Mortar
Unlock Crook
Unlock Warden
Discovered all potions
Spare 200 enemies
Clear the Madblocks
Clear the Voidblocks
Enter Turbo Slammer 2