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