Venice Canalside cafe

your requirements let out my two suggestions from personal use.

One is near the University and S. Pantelon, excellent coffee and pastry and fresh juice, but it isn't canalside and the area can have traffic walking past.

The other is way over in Castello, near Campo San Lorenzo. More of a bar, canalside (2 canals), not much traffic boat or people, but nowhere near Rialto, and I am not sure I remember any outside tables.

Sorry.

(you may see a Brunetti connection, but both as good as described, IMHO)

Ristorante da Raffaele has good food and outdoor seating next to a canal and a bridge. Closer to San Marco than Ponte di Rialto - that bridge was as crowded as Disneyland. For a really special ($$$) anniversary dinner we ate at Gio's whose terrace was directly above the Grand Canal. Superb food and views.

Steve T doesn't seem to be looking for a place to have a full meal, just a coffee stop for the morning. Unfortunately, I'm not a cafe-sitter and cannot help.

I would skip Rio Marin.Yes, it’s on a canal and there is outside seating, but their pastries aren’t as good as others and there is NO shade. Our favorite ended up being Pasticceria Trevisan-outdoor seating under cover. It isn’t real close to Rialto, but it’s worth going to-try the pincia-also we liked Pasticceria Rizzardini. Closer to Rialto but no outside seating and no canal. You really probably can’t go wrong unless it is on a main thoroughfare, it may not be quite as interesting. P.Rizzardini is on a thoroughfare, but well worth visiting for their pastries and coffee. Enjoy.

Maybe try one of the two cafes in Campo San Barnaba, Dorsoduro.

Nigel, thanks for your tips.
SJS, thanks for the tip on Rio del Marin, and for your suggestions.
Cynthia, thanks for the dining tips. We need places for dinner as well, so I'll look into these.
Aussie, what are the names of the cafes you recommend in Campo San Barnaba and Dorsoduro?

There is a good restaurant on Rio Marin-Osteria AE Saracche. They do have outside tables on the canal. Reservations definitely needed and I think they’ve gone to a two seating an evening format-early dinner and late dinner.

Two cafes in Campo San Barnaba. One is the Ai Artisti, about 20 metres back from the canal, Rio San Barnaba.
I don’t remember the name of the other cafe, but it is quite obvious. The de-consecrated church of San Barnaba now houses a display dedicated to the inventions of Leonardo da Vinci, all sorts of mechanisms.

In the 1955 movie Summertime, the directors had Katherine Hepburn fall into the Rio San Barnaba. It took her ages to recover from the resulting bacterial infection.