Safe Haven

Walkthrough
Talk to Leuvaarden to get the quest, then use the ferryman to go to the swamp. There is a fireplace nearby. Meditate until midnight here. Then, roam the small area between the boat, the fireplace and the woods. One-by-one drowners will appear. Keep killing them until you get a status update on the quest.

The Merchant
The merchant Leuvaarden apparently has some work for a witcher. I can find the merchant on the Dike, where he conducts business in daytime. If I mention our mutual friends, I will easily get the assignment.

Drowners in the Swamps
Leuvaarden offered me 400 orens for killing drowners. I should use the boat to get to the swamps and get rid of the monsters that have been haunting the harbor at night.

The Reward
I killed all the monsters - time to collect my reward from Leuvaarden. I will find him on the Dike. (500 XP)

Quest Completed
I collected my payment - working for Leuvaarden is a sheer pleasure. (400 orens, 2000 XP)