The Sword, Famine and Perfidy The Witcher 3 Guide

The hut on the beach

Above Novigrad you will find a small hut surrounded by a group of drowners (level 34) (M1,10). Go inside and on the left side you will find a corpse and a letter near him. Then destroy the barrels with Aard sign. This will allow you to open the hatch to the basement, where you will find a body with a rusty key and a letter that triggers the quest.

After destroying the barrels you will notice the hatch in the floor

In the chest you will additionally find 100 florens, don't miss it. After reading about the quest from the note go on a hunt for the sunken ship.

The treasure is hidden in the chest underwater

The ship - or rather a boat - can be found nearby, on the east near a small island. The closed chest contains partially random low value items - runes, alchemy ingredients and some coins.