We’ll, that’s a timely question. It was one of the few times Viking dropped the ball. On the 20th we had 2 excursions. During the day a lengthy tour walking in Venice, during which, the Viking “escorts” turned it over to a local and knowledgeable guide who took longer than expected. This caused a relatively short allotment of time between the day excursion and our evening gondola excursion so I asked the “escort” taking us back to the water taxi if we should just wait in Venice for the evening gondola excursion instead of only having around 30-45 minutes at the ship before the scheduled 2nd trip to Venice that day. She said “you’ll need to go back”. You’ll have enough time. So we trudged on back, rushed to clean up a bit and grab something from the World cafe before heading back to the bus for trip 2. We rushed ourselves to only find that the new “escorts” were waiting and waiting to find missing passengers who were supposed to be on the bus. After waiting over 20 or 30 minutes past the scheduled time we left with just 6 passengers. Very odd since I knew there should have been many more. When we arrived back at St. Marks square we were told we are going to meet some that were waiting there. Apparently some others who had different day excursions were told “ No do t go back, just wait in Venice. Those waiting in Venice kept asking why is it taking so long, not knowing the “escorts” were late because we waited at the ship for them. Anyway that happened.
BTW, both excursions were good and I don’t have info on if those just using busses for “on their own” had delays. I expect they did not as there were plenty of busses.
Regarding the 21st disembark day, those of us on our own were given the option the day before to choose the option of having Viking arrange a private water taxi to whatever hotel in Venice we had booked. This was at a premium price but worth it to us. It appeared their were at least more than another dozen couples who chose it also. It was a shorter ride as I said and we were totally taken care of by Viking with the private water taxi who did an excellent job helping us to the hotel Rosa Salva( highly recommended it).
Hope this helps.