We went with Viking in October to Venice, on our turn around day there was only one free shuttle to Venice which left at 8:30, it gave you about 4 hours in Venice, however, if you want to stay longer you can get back to the ship on your own, you need to ride the water bus up the grand canal to the old cruise port where viking is taking all the passengers getting off their flights, meet up with them and get on the viking bus to the cruise ship. We stayed in Venice until 5 and were glad we did, we were there at a slow time so were able to walk right in to the Doge's palace and do a tour. We were able to buy tickets on the spot, we also waited 45 minutes in line to see St Marks