Here is the full list of all 27 Aquaria achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Find all the recipes in the game.
Find all the Ancient Turtles.
Travel to all the areas of Aquaria.
Learn all the songs in Aquaria.
Rescue all the lost souls.
Defeat Mom and Dad.
Beat the Arnassi race in less than a minute.
Find all the health eggs.
Reach the Frozen Veil.
Discover two peculiar-looking fish...
Enter the belly of the Whale.
Defeat the King Jelly.
Defeat the Rock Crab.
Defeat the Mantis Shrimp.
Devour a Parrot.
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Defeat the Priests.
Defeat Octomun.
Fling a Monkey.
Defeat Mergog
Reach the Sprite Cave.
Dive into the water from a certain high location...
Ride Ekkrit for a minute.
Kill the Coward.
Reach the Veil.
Devour 6 creatues in a row.
Reach Open Waters.