I was there about two years ago in June and it didnt smell at all. Venice was siick but I definately would not get in the water. The best part was when I was there they were filming James Bond Casino Royale and we got to watch them do it. It was really cool.
they have cleaned the water up alot compared to years ago. its really not that bad cause people can't just dump all there shit into the canals. (claim alert) ive been there and it was the most amazing place i have ever been (claim alert)
venice canals are a no wake zone since all the buildings are right on the water but ive been there it smells really bad but i dont think the water is polluted because the city was built on a swamp so it is naturally that color but in the middle ages thats were they but their sewage