Heroes of the Seven Seas

Story related, cannot be missed.

When you first arrive on the island, head towards the tribe for Merfolk and you'll see your ship to the left. It's hard to spot, but there's an icon you can select to leave the island. Selecting to leave the island will take you to the next level called, "The First Cannon". It's this area where you'll get the final three upgrades to your pirate ship. One of these upgrades your pirate ship's forecastle with the Mermaid Bow Gun. This is the strongest weapon in the game as it can destroy smaller enemy ships in only one hit. The Mermaid Bow Gun can be used by simply pressing the button, but it should be noted that it takes time to recharge. Whenever it's fully charged again, you'll know as the front of your ship will be glowing blue.