USEFUL INFO: How to go from the ship to Piazza S. Marco
Venice obviously is all developed on water and so to go anywhere you need to catch a boat. You can either hire a water taxi, which you will find right next to your ships pier, or you can use the great city water public transportation.
To reach the hearth of the city, you can take the Alilaguna BLU line water bus
from the cruise ship terminal (in Italian “terminal crociere”) to "San Marco" stop just in front of the very famous square.