May I recommend this timeshare operator?
http://www.vaporettovenice.com/
You can leave there for minimal three days in a real palazzo. I prefere apartements at Dorsoduro district (Salute Church).For example the Studio D148S (40sqm) just in the near of the Guggenheim Museum, the Accademia Bridge an 500 yards to the Zattere vaporetto station, where the water shuttle from the airport stopps.
Here is an other information from the webseite:
• if you are calling from the States, Canada or Mexico: 1 866 212 5009>
Have some nice days in the loveliest town i know.
Uwe