One more thing. If you can afford it, when you leave Venice, take a water taxi to the airport. The view and the experience will cap off the 24 hours nicely.

....Wish I could blindfold people and have that be everyone's first view. It is overwhelming......

That was my first view. I was blown away! Again it was a day trip. I've been back four times staying a fortnight at a time. There is always something new.

Like ssander said. Getting off the train and walking out to the Vapretto. Tears came to my eyes. In a good way.

DO IT! Venice is so unique and beautiful. One day will be a great way to get a taste of it and see if you want to come back again...I really think it is worth it.

Another YES vote. Subtracting one day of six from London for a day in Venice... no contest imho!!!