ACTV runs the vaporetti and other public transport services both in the lagoon and on terra firma. Travel cards are extremely useful since the basic fare for one vaporetto journey is typically €7.00. There are other versions available, including those offering discounts for youths under 29. The vaporetti uses an honour system, meaning you are expected to validate your ticket at the stop before boarding, but there's nobody making sure you do so (except at the busy Piazzale Roma stop), and checks on the crowded vaporetti are extremely rare.