The next mission will start at the docks. Speak with the overseer and choose "The Hard Way". Approach the ship wheel to learn how to navigate the ship.
Optional objective: Do not take any damage.
Start off by pressing the jump button to go half-sails. Pressing the button again will set the sails completely and let you reach full speed. The interaction button lets you slow down.
Your target will be the village marked on the map with a green dot. Sail there while avoiding hitting any rocks. Only that way will you be able to complete the optional objective. For better manoeuvrability, go half-sails.
After getting close enough to the target, press the interaction button twice to stop the ship.
After a short cutscene you will once again set sail, though this time armed with a set of cannons. There are two types: the cannon volley and the swivel guns.
The first one is used with the free run button and the second with the aim button. With the swivel guns, be sure to let go of the button only after the sight changes to red. Use the cannons to destroy two wrecks marked on the map. The cannons will shoot where the camera is looking.
Optional objective: Successfully brace when attacked - 3.
Optional objective: Use the swivel guns to destroy ships -2.
Optional objective: Completed all the constraints in one playthrough.
Afterwards sail onwards and you will be ambushed by enemy ships. You need to destroy them by facing them sideways and using the cannons. For the additional objectives, you need to destroy both with the swivel guns and avoid being hit by sailing with the wind three times.
To destroy the last ship, shoot it twice with a cannon volley and afterwards finish off with the swivel gun. Soon afterwards the mission will end.