Shipbreaker (quest)

Shipbreaker is a quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
While exploring Far Harbor, you may randomly pick up the Shipbreaker's radio frequency, immediately starting the quest. Follow the signal to a patch of land near a ruined house, where you will find Shipbreaker, a unique fog crawler. Once the fight is over, you are prompted to speak to Old Longfellow. He will talk about how he has been searching for Shipbreaker for years. Tell him that Shipbreaker is dead, and the quest will complete with you earning a unique harpoon gun that Old Longfellow was saving to deal the final blow on Shipbreaker with.