The Fish Market is in a square surrounded by Belediye Cad., Hukumet Cad., 96 Sokak and 97 Sokak.
Get off of the Water Taxi and start heading towards the rock tombs. You'll cross a one-way street on which the traffic is running left to right, that's Ataturk Cad., The next street as you go towards the rock tombs is 96.Sokak.