Yes, you must pay for buses in Venice, but it is important to distinguish between the "water buses" and the "land buses." The water buses, known as Vaporetti, are the primary mode of transport within the historic island city and are quite expensive, with a single 75-minute ticket costing around €9.50. On the mainland side, in areas like Mestre and Marghera, there is an extensive network of traditional wheeled buses and trams operated by ACTV. These land buses are much cheaper, usually around €1.50 for a single trip. You cannot buy tickets directly from the driver on most routes; you must purchase them in advance from "Venezia Unica" kiosks, tobacco shops (Tabacchi), or through the official AVM/ACTV smartphone app. For tourists, the most cost-effective method is often a 24-hour, 48-hour, or 7-day travel pass, which covers both the vaporetti in the canals and the land buses in Mestre. Always remember to "validate" your ticket by tapping it against the electronic reader before boarding, as ticket inspectors are frequent and fines for unvalidated tickets are steep.