The price for the water taxi depends of the time of the year, sometimes in summer prices are higher than in winter or spring. The highest price for one way transfer from Lapad to old town port should be 100 hrk maximum. This price is for Uvala Lapad point. If you take water taxi from Lapadska obala or any points in Babin Kuk which is also Lapad the journey is longer so the prices will be higher but not much much higher.