We pre booked travel cards and toilet tickets through Venice Connected. This was not worth doing. The ticket office where the ship docked would not do the internet vouchers so we had to get the people mover, (1.00 each way, correct change only which caused long queues especially as a Costa cruise ship was unloading) which runs TRONCHETTO-MARITOMO- (cruise terminal)- PIAZZA LA ROMA) in to Piazza la Roma where we stood in a very long queue to be told we were in the wrong queue. We then went to where we were told to go to find the Venice connected window closed. To cut a long story short, ourselves and other people off our cruise who had bought the same deal, we managed to get our tickets through the normal ticket booths but not without problems. Took nearly 1 hour of queuing and arguing to get our 36 hour travel ticket. The hassle was not worth the small saving (1.20) we made by pre-booking online. Toilettes are available at every cafe, restaurant and museum so they were a waste of money. We bought a book of 10 and used 2 just to say we had.
My advice is get off the cruise ship and walk to Tronchetto which is only 15-20 mins away and buy your tickets there, use the people mover if you wish to get to Tronchetto but it is an easy walk. You can then get on the ACTV No 2 Vaporetto (water bus) there. Using this route you can ride down the grand canal to St Marks Sq, a tour in itself. Calculate the time you will want to travel around Venice. We bought the 36hr card (more than we needed) but some people only bought the 24hr card and could not understand why they could not get on the Vaporetto to return to the ship. You have to validate the card (like go card swipe) before getting on a water bus. It will not let you onto the jetty if your time is up. Passes were 18.00 for 24hrs, 23.00 for 36 hrs or 6.50 for a rtn to St Marks Sq. Passes are well worth the money. We used ours to just ride around the islands, getting off where or when we fancied, sitting by the water to have an evening aperitif and watch the sunset on St Marks on the other side of the water, or go to Murano to see the beautiful glass works. We also jumped off at different stops just to wander around. A lovely way to see the other side of Venice. We did the Doges palace after 2 pm when all the tours had left and still had plenty of time to see everything.
Be aware the ACTV No 2 runs from two different jetties. if you want to rtn via the Grand Canal you need to get the No 2 back from St Marco jetty (up from St Marks Sq) or get on the No2 at Zaccaria (down from St Marks Sq) for a different ride back to Tronchetto. We used this one evening, getting off at Palanca on Giudecca Island to sit in the shade, have a drink and watch St Marks Sq fade in the sunset. Beautiful and what a holiday should be.
There is another water taxi line which runs from where the cruise ship docks at Maritima called Alilaguna. This is a private company and they do not have as big a route as ACTV and do not run as often. They are more for getting to and from the airport than riding around Venice. A young couple who bought Alilaguna travel cards did not speak highly of them, said they were a long time between buses and did not go everywhere they wished to travel. I believe a lot of cruisers used this company as they were near the cruise terminal. Take the extra time and walk to Tronchetto to get ACTV tickets, you will be glad you did.