Here is the full list of all 17 Buccaneers! achievements.
Reach player level 20.
Fully upgrade a ship.
Acquire a Three-Decker.
Complete Act 3.
Have a full fleet of four ships (excluding temporary ships).
Complete Act 2.
Rename a ship.
Have a fleet of two or more ships (excluding temporary ships).
Complete Act1.
Capture any town by defeating its fort.
Choose which faction to join.
Capture a ship.
Steal a ship from an enemy harbour.
Conquer the Caribbean for Britain.
Conquer the Caribbean for France.
Conquer the Caribbean for Spain.
Conquer the Caribbean for the Buccaneers' League.