Witcher 3 Precious Haul Walkthrough
Start Location: This is started from a Hidden Treasure marker located just southeast of the ‘Tor Gvalch’ca’ at the northern end of the island of Undvik. This is on a beach just before reaching the mist we need to enter during the ‘Isle of Mists’ quest.
After locating the beach with the Hidden Treasure marker, you’ll see it is indicating a beached ship. Investigate this wreck and on the main deck you’ll find a dead body. Use Geralt’s Witcher Sense to examine these human remains.
Upon looting the body you’ll receive Traveller’s Notes. Read the Traveller’s Notes item in the Key Items section of the inventory. This will trigger the ‘Precious Haul’ side-quest.
You’ll notice that there is now a yellow search area off the coast just to the north of the corpse’s location. Swim or boat out to the objective location zone and hop into the water. Kill any of the nearby Sirens that come after you with your crossbow from under the water.
When it is safe to swim, activate your Witcher Sense to look for a red chest on the ocean floor. Find and loot the chest to complete the side-quest. It contains some random gear and crafting reagents along with a small sum of Florens.