Optional objective: Limit environmental damage - 25%
After the mission begins, sail in the designated direction while avoiding nearby rocks. Get to open sea and therefore you will complete the optional objective.
Keep sailing with the wind and eventually you will be attacked by the Somerset with smaller ships. Start off by eliminating the ships on the right with a quick salvo and swivel guns and afterwards eliminate the enemies on the left similarly.
Leave the Somerset for the end. Shoot it a couple times and a white circle will appear. Shoot it with the swivel gun and the mission will end.