We were in Venice in May of 2000. It was a 2-day stop on a 12 day cruise on the Splendor of the Sea.
We just caught the tail-end of the 60-Min. story on Venice and kicked myself for not tuning sooner. So we didn't get the whole thing.
What I can say is that when we were there, we were able to go anywhere we wanted without trouble. No shops were flooded, etc. However, upon arriving in Venice, we booked a 2 hour tour of the city by water and the guide was talking about the terrible high tides they get occasionally. Everything comes to a complete stop. She told us the frequency of these occurrences, but, like a big dummy, I was not paying her the attention she deserved - I was just overwhelmed by the beauty that was Venice.
You will have a marvelous time on your cruise - enjoy! (Wish we were returning again this year!)