A Walk on the Waterfront is a secondary quest in The Witcher 3: Wild Hunt.
Walkthrough
Near the water wheel to the east of Novigrad Docks, you'll find a man being harassed by some bandits. If you don't intervene, the bandits will soon kill the man, and thus not able to do the quest.
Intervene and eventually the man, Ginter de Lavirac, will ask you to "take a stroll" with him, protecting him as he makes his way down the port. Note that backing out of the conversation at any point will mean not being able to continue the quest as Ginter will then leave.
If you agree, along the route the pair is attacked by several groups of bandits, with each group seeming to know who the man was, and that he would be coming that way. Important: you must keep Ginter alive during these fights. If he dies, the quest will fail.
Once Geralt accompanies the man to his destination, it is revealed that the man is a fisstech dealer who is meeting his supplier. Answer however you like to the gardener comment, and eventually it'll come down to you defending Ginter or not. If you agree, the suppliers will back off and agree to the stated price and Ginter will reward you with 50 
and 10 
. However, if you disagree and back out, the suppliers will kill Ginter but reward the same amount. Regardless, the quest will then complete.
Journal entry
- A certain nobleman asked Geralt for a bit of assistance. He wanted the witcher to accompany him on a stroll through a rather dodgy part of Novigrad. The richman's clothing alone would get him killed in that quarter, so Geralt agreed to help.
- The witcher defended the aristocrat from bandits as he indulged in a bit of slumming. Not his most glamorous contract, but neither was it the worse thing he'd ever had to do for coin.
Objectives
- Escort the nobleman.