At first I thought this game was only destroy other ships and win, but there is much more to it than that. There are different types of battles, and all have a very specific purpose.
Lost Treasures - There are two teams that search for a sunken ship with treasure. You have to destroy all the enemy ships and retrieve the treasure to be victorious.
Royal Caravan - There is a Convoy team and a team of Attackers. The Convoy has to safely escort at least one caravan in order to win. The Attackers must destroy all of the caravan.
Port Siege - Each team must get to the enemy's port first in order to win, while also destroying all enemy ships.
Pirate Bases - Each team must capture the enemy's base and destroy all ships to win.
Fleet Battle - Destroy all enemy ships.
So the game's main focus is PvP, but there are other aspects of the battle to focus on while playing. It adds strategy, which makes any game interesting.