Cabin boy
Complete a level in Normal mode

Empowered
Obtain a powerup

Fresh fish
Kill an enemy

Slippery
Finish a level losing no lives

All star
Obtain 3 stars in a level

Shallow waters master
Complete the first chapter: Shallow waters

Catch-and-release
Complete a level with 5 enemies alive

Reef ahead master
Complete the second chapter: Reef ahead

Underwater volcano master
Complete the third chapter: Underwater volcano

Arctic fire master
Complete the fourth chapter: Arctic fire

Question of time
Complete a level in Time Trial mode

Unfrozen
Kill an enemy while he's inside an ice block

Shellfish lover
Finish a level with 2 crabs still alive

Like this big
Complete all chapters in Normal mode

Right on time
Complete a Time Trial level with only 1 second left

Just about time
Complete all chapters in Time Trial mode

Underwater legend
Complete Normal mode with all the stars in all the levels

Lord of the seas
Complete Time Trial mode with all the stars in all the levels