The most famous of the vaporetto routes in Venice is of course the number 1, which plies up and down the Grand Canal (and then all the way out to the Lido). If you take only one vaporetto ride--and at €6.50 a ride for visitors, one is all many people do take--you can't miss the number 1.
But today I'd like to put in a plug for the number 62, which runs with just a few stops from the Lido to Piazzale Roma via the Giudecca Canal--or any of the other lines with high numbers and, most important, low-riding sterns.
I took the 62 yesterday for the first time and sat in one of the four outside seats in the very rear of the crowded boat. It was cold, loud and smelly, but what a marvelous ride! On the 62, and any of the other lines that use this particular model of vaporetto (the number 1 never does), you ride so low in the water that you have a swell's-eye view of the city. Seated back here the lower half of your body seems to be below the water line. You can trail a hand in the water if you want (though I don't recommend it).
The engine rattles and grinds almost beneath you, rising to such a raucous pitch during acceleration that the next sound you expect to hear is--silence, after it has seized up and cut out for good. Diesel exhaust rises behind you to the height of the roof and sometimes visits you in your seat--as does spray from the hard working rotors. The boat's wake billows to either side of you, iridescent in the late sunlight, and when another boat passes by in the opposite direction waves seem to crest as high as your chin.
I don't suppose it can be called a romantic ride--at least not in a conventional sense. But I can't imagine another form of public transportation anywhere that offers a better view of the city it serves. Dying to take the perfect picture of San Giorgio Maggiore? Don't bother with the famous vantage point on the Piazzetta or Molo, take the 62 as the sun is setting.
When you're riding this low the lagoon finally gets its full deserved due. Arrayed along a high horizon line, the city's most famous buildings become merely a spectacular backdrop to the shimmering water that kept the Republic impregnable for over 1,000 years. Before there was anything else there was the lagoon, and unless you can afford to spring for a long far-ranging gondola ride, the lagoon is most perfectly (and affordably) foregrounded when you're riding in the rear of a low-slung vaporetto like the 62. I can't wait to go on it again.