On paper this scene should not work. A floodlit white stone bridge sits against a sky with no light in it at all, the water throws back a dozen point sources at different colour temperatures, and the whole thing has to be held still by hand because you are standing on a floating pontoon with people moving past your shoulder. Start with why the tripod is not the answer here. The banks along this stretch are narrow, busy well past midnight, and the good vantage points are all working infrastructure: vaporetto stops, taxi pontoons, delivery moorings.