The best way that I have so far found to visit Venice is to stay outside the town and travel in by bus. Fortunately there are campsites that allow us to do this and as can be seen in this video, The Serenissima is right next to the bus stop and from there it is a 13km journey. A single ticket from here costs EUR1.50 which will take you to the Piazzale Roma and from there you are already within the fabled city. Motorised vehicles cannot get any further into Venice than here. If you are feeling particularly fit, you could try by bicycle too but it is not a nice journey along busy roads with a lot of heavy traffic.
The campsite is located near the road so it has convenient access but it is down a side street so it is quiet.