Here is the full list of all 21 The Aquatic Adventure of the Last Human achievements.
Unlock hardcore mode
Complete the game
Defeated The Guardian
Find all upgrades
Defeated The Heart of the City
Defeated The Experiment
Read all Holotapes
kill 100 fish
Defeated The Chain Gang
Defeated The Parasite
Defeated The Tranquil
Defeated The Defiler
Defeated The False Light
Defeated The Forgotten One
Defeated The Fathers
Defeated The Worm
You died.
Incapacitate the Tranquil
Complete the game without any upgrade crates
Complete Hardcore mode
Complete Boss-rush Mode