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