Optional objective: Limit damage to La Belladonna - 50%
This time you will have to protect La Belladonna. For full synchronization, you can't let it lose more than 50% of its health.
Optional objective: Sink more enemies than La Belladonna - 11
Keep sailing with the ship and you will be attacked by the British. You need to destroy their ships as fast as possible so that you can win with La Belladonna. Smaller ships are easy to destroy with the swivel guns.
After the first attack, you will be attacked once again but this time a frigate will be amongst the enemy forces. Try destroying it in the first place, attacking the other ships only occasionally.
After fighting off this wave of enemies, Belladonna will be attacked by a ship of the line. Quickly press the inventory button and choose the chain-shot. Use the free run button to shoot it at the enemy and therefore destroy the masts.
Afterwards swim to the ship to board it.
Optional objective: Kill the officer within the given time - 1:00
Onboard the ship of the line you will have to kill its officer. To reach him, go round the nearby mast from the right side. His death will end the mission, but if you manage to kill him in less than a minute, you will also complete the optional objective.