Here is the full list of all 21 Pacifish achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Complete 50 thousand catches
Find all five shells
Find the Black Orb
Own all tackle
Unlock Dam and Sky fishing
Own all fishing poles
Defeat all bosses
Reach Fisher level 100
Earn 500 million coins
Eat 10 million fish
Earn 50 million pixels
Defeat 50 thousand enemies
Reach fight area 100
Hatch 10 million fish
Craft 20 fishing pole mods
Reach Market level 50
Get 1000 matches
Spin reels 50 thousand times
Use 1000 bait
Reach Swimmer level 10
Acquire Sam's journal