Leave the ferry and head to Steiner's Workshop. When you are there head left and use the stairs that are ahead. You reach the square near the station (on the left) -go to the opposite side (deeper in the screen) and go down the stairs to reach the square in front of the town hall where a protest takes place: citizens of Valsembor are protesting against Youkols.
Speak with one of the female protesters - the stout woman in beige coat that holds a protesting board (the one farthest to the left). You learn a few things about the mayor.
Go up the stairs to reach the platform, where the mayor is standing. Talk to him. If you want Kate's mission to finish successfully (and to simultaneously gain the Lobbyist achievement), pick the dialogue options, which will not antagonize Buliakin (3, 3, 3, 1, 3). Truth be told, in both cases our hero will need to perform the same task, but when granted the mayor's permission, she will gain certain aids - the supervisory commissar's note.
(If, in addition to that, during the moment when you try to convince the mayor you use the information received from the protester - option no. 2 - you receive Martingale achievement - unless you already got one during a conversation with the captain).
Afterwards, head back aboard the ferry via the same route, once there you should head to the bridge. Discuss the situation with the captain. He will point Kate towards a shed at the end of the seawall, where she can prepare to go underwater.