Here is the full list of all 31 The Oil Blue: Steam Legacy Edition achievements.
Reclaimed your first island
Reclaimed a second island
Reclaimed a third island
Reclaimed a fourth island
Reclaimed a fifth island
Completed the tutorial
Achieved Rank 48
Achieved Rank 45
Achieved Rank 42
Achieved Rank 40
Achieved Rank 36
Achieved Rank 32
Achieved Rank 28
Achieved Rank 25
Achieved Rank 22
Achieved Rank 18
Achieved Rank 15
Achieved Rank 12
Achieved Rank 10
Achieved Rank 9
Achieved Rank 8
Achieved Rank 7
Booted up the Oil Blue Achievement App
Reclaimed a sixth island
Reclaimed a seventh island
Reclaimed an eighth island
Reclaimed a ninth island
Reclaimed a tenth island
Reclaimed an eleventh island
Reclaimed a twelfth island
Achieved Rank 5