SKULL KEY

 Port is the left side of a ship, Starboard is the right. 

Where would these two meet?   Go there. 

Scroll down for more hints.

Go on top of the pirate ship and remove the carpet infront of the wheel. 

Put the skull key in the green hole that you find that fits its outline. 

This will release a door on the ship, inside is a key.

That key unlocks a lock under the green velvelt little door.