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