Venice has no single harbour. Four separate boarding addresses send out four different kinds of day, they sit on opposite sides of the city, and the walk between two of them is twenty minutes through the busiest streets in Italy.
San Marco Giardinetti, the pontoon strip immediately west of Piazza San Marco in front of the Giardini Ex Reali, is where most group island tours load. Its neighbour a few metres along, San Marco Vallaresso, is a different pontoon with a different name on the sign — the detail that costs people a departure.
Riva degli Schiavoni runs east from the Doge's Palace and carries numbered private pontoons; several operators meet in front of Palazzo Cornoldi at number 4142, eight minutes from the piazza, where piers 1, 2 and 3 sit together. Just west is San Zaccaria, the ACTV interchange for lines 4.1, 4.2, 14 and 15 — a public stop, not a tour pier.
Fondamente Nove, on the north shore facing San Michele, is the public gateway to the lagoon: ACTV line 12 leaves here for Murano Faro, Mazzorbo, Burano and Torcello, lines 4.1 and 4.2 make the shorter hop to Murano Colonna, and almost no guided tour boards here at all.
Tronchetto is the artificial island at the road end of the causeway, used by coach-linked operators because a bus reaches it; the People Mover links it with the Marittima cruise terminal and Piazzale Roma for €1.50. Punta Sabbioni, across the Lido inlet, is the pier for the round-trip boat with free parking at $20 and for ACTV line 14, which reaches San Zaccaria in 35 to 40 minutes via the Lido; line 15 skips the Lido in 25 to 30, but runs only from April to October on a few weekday sailings.