The Great Hunt

The Great Hunt is a quest in the Far Harbor add-on for Fallout 4.

Detailed walkthrough

 * The Mariner will tell you about a mysterious creature that has been destroying boats leaving and coming into Far Harbor.
 * She will then ask you to take to your boat and she will take to hers. Before you board you are stopped by Avery, who tells you that it is an old myth and you're wasting your time.
 * You will then board your boat which has already been programed by The Mariner to go to Red Death Island.
 * Once you arrive you will look for the Red Death.
 * Talk with The Mariner about finding Red Death, and then it will appear in front of you. (It's a baby mirelurk)
 * Vanquish the Red Death! (Takes 1 or 2 hits)
 * The Mariner will be very disappointed, but will still reward you with the Legend of the Harbor, a unique version of the Fisherman's outfit. She will ask you if you want to tell the truth about the monster or lie about. You will then get back onto your boat and sail back to Far Harbor
 * You will then Receive a hero's welcome from the town's people depending on if you choose to lie or not.