Hull Breach

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

Part 1
Go to the Mariner; her office is to the immediate left upon entering Far Harbor. She asks the player character to find her a special set of tools to help improve the capabilities of the Hull. They can be found in Eagle's Cove Tannery. The tannery is occupied by ghouls, but is not too extensive. Recover the tools, and return. Exiting the tannery through either the front door, or a back door, will lead to the player character meeting a man named Machete Mike, who claims the tools are a rare set of Pelman's. He offers 2000 caps for them, wherein the player character accepts the offer, but fails the quest; or, refuses the offer without any further conflict. Mike may be killed after refusing his offer, netting the player around 3000 caps, but will restrict the player from advancing in the quest line. However, if you try to pickpocket Machete Mike he will become hostile and attack you, at which point you can kill him in self-defense and loot the caps from his body without being penalised (inconsistent), and you can continue with the quest. Return the tools to the Mariner, and receive the caps and experience. The next time Far Harbor is visited, large spiked barriers will be found on the outside of the Hull.

Part 2
During, or after completing, Rite of Passage, the Mariner will offer a second opportunity to improve the Hull even more. Dialogue with her reveals that she desires to complete it as soon as possible, due to the doctor diagnosing her with an incurable illness. She sends the player character to the MS Azalea, to clear it of the occupying trappers. After killing the leader, Bilge, the Sole Survivor returns to Far Harbor and accepts the caps and the Mariner's respect. The next time Far Harbor is visited, two large sections of the Azalea's hull will have been attached to sections of the Hull.

Part 3
During The Changing Tide, the Mariner will offer one last chance to finalize the Hull's defenses, primarily against the corrosive acid of mirelurk queens. She sends the player character to collect three Mirelurk carapaces to coat the Hull with, making it acid-resistant. While any Mirelurk will do, a particularly rugged type can be found at Haddock Cove. Collecting the carapaces takes the Sole Survivor back to the Mariner, who thanks the player character, and rewards them with a Legendary harpoon gun, of varied effects. The next time Far Harbor is visited, three overhangs built out of the carapaces will be added along the walkway above the Hull.