Here is the full list of all 25 Flying Shark achievements.
Hit a squadron of yellow airplanes to get a bonus
Upgrade your weapons one time
You have achieved your first of many losses to come
Play a hundred games
Get terminated a thousand times
Fire one million buillets of any kind
Defeat ten thousand enemies
Upgrade your weapons a thousand times
Upgrade your weapon to the max
Turn the first boss in the game into dust
Crush the spirit of life out of the second boss
Return the third boss to its maker
Put the fourth boss six feet under
Slaughter the Final Boss
Eliminate the first boss without assistance
Eliminate the second boss without assistance
Eliminate the third boss without assistance
Eliminate the fourth boss without assistance
Eliminate the final boss without assistance
Complete the game using only one credit
Complete the game using only one credit without assistance
Used a bomb in gameplay
Pick up 100 bombs in gameplay
Pick up a 1up item
Hit a squadron of yellow airplanes to get a bonus ten times in one game