Mario & Luigi: Brothership doesn't contain many boss fights, but every once in a while the game will throw a tough obstacle in the player's path. One of these is Gobblick, the guardian boss of the first Great Lighthouse Island. This island and boss unlock after the player completes all prior islands in the Lushgreen Sea.

These Reefs are found all around the seas of Concordia, so you have some work ahead of you before you can find them all. Note as well that some of the Hidden Reefs are only unlocked later on in the game,