My suggestion - Nico's on the Zattere. You'll be sitting over the water, watching all the nautical endeavours that keep Venice afloat and on an even keel. Water taxis, maybe a police boat or fire boat blasting past, perhaps a cruise liner (wash your mouth out, Peter), a Fedex branded delivery boat perhaps.
Order Negronis all round. They'll blow your head off. Sure, Ern Hemmingway and his drinking buddy Scott Fitzgerald patronised Harry's. Unfortunately many people still think it is the place to be, and think that Bellinis are all the go.
I would never enter a bar that I could not see inside before I entered. And you can't see inside Harry's bar.