Unlock the following uncharted islands by performing the corresponding tasks:
HOW TO UNLOCK
Collect the five pieces of Captain Taint's map. Start the quest to help him get his treasure. He tells you it is on Cliche Island and that a Mutinous Captain may have it. You can also find Mutinous Pirates with the captain on X Island. Just west of X island is Chicken Island, which has the parrot feather required for a different quest. Start at the dock at Chicken Island, then move straight west until you see a small island slightly to the north. Dock there to find Cliche Island and a treasure chest.
Move south from the western side of Spider Island.
After invading the North Pole, get on your ship and travel south from the dock. Look for a few rocks sticking out of the water and a spear with a skull on it.