Complete the following tasks to unlock the corresponding achievement.
To view your achievements and stats in Steam, select "Community", 
then "My profile", then "View all my games", then the game and view stats. 

A New Chapter...     - Reach Open Waters. 
Boom Shrimp          - Defeat the Mantis Shrimp.
Bucking Bronco       - Ride Ekkrit for a minute. 
Combo Eater          - Devour 6 creatures in a row. 
Dethroned King Jelly - Defeat the King Jelly. 
Divorce              - Defeat Mom and Dad. 
Explorer             - Travel to all the areas of Aquaria. 
Feather-Mouth        - Devour a Parrot. 
Gullet               - Enter the belly of the Whale. 
Healthy              - Find all the health eggs. 
High Dive            - Dive into the water from a certain high location.
Mass Transit         - Find all the Ancient Turtles.
Mergog Defeated      - Defeat Mergog
Monkey Flinger       - Fling a Monkey.
No Escape            - Kill the Coward. 
North Pole           - Reach the Frozen Veil. 
Octogone             - Defeat Octomun. 
Passed Through       - Reach the Veil. 
Rock Crab Rocked     - Defeat the Rock Crab.
Songstress           - Learn all the songs in Aquaria.
Speed Racer          - Beat the Arnassi race in less than a minute.
Spirit Battle        - Defeat the Priests.
Super Chef           - Find all the recipes in the game.
Uniter               - Rescue all the lost souls.