Thank you to Winckelmann for the explanation of the words carved into the Istrian stone at the edge of the Riva degli Schiavoni:
I found them! When I commented yesterday I hadn’t realized that they are still on the water and thought they were somewhere in the pavement of the Riva. The reason is that they are in that section of the Riva which was in the past centuries already as large as today, as one can see in the paintings of Canaletto or Carlevarijs. Anyway, here is the translation (pardon my English!):
1): “26 aprile 1799. Stazio di piedi 80 per cinque burchi da vino”: April 26th 1799. 80 feet dock for five boats for the delivery of wine.
2): “Fine di stazio dei abitanti della Brazza e di Lisina”: End of the dock reserved to the inhabitants of Brazza and Lisina, that’s to say Brac and Hvar, islands of the Dalmatian coast. Remember that Riva degli Schiavoni means Dock of Dalmatians!
3): “Stazio di cuna di Pirano”. This is not completely clear to me. Stazio means dock and Pirano is a city in Istria. “Cuna” could be a kind of boat (it properly means cradle), or maybe “Stazio di cuna” means something I don’t know.