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