Here are few instructions on how to get to the ISMAR-CNR Institute by Vaporetto.

From the railway station or from Piazzale Roma, take LINE 1 in the direction of Rialto-San Marco. Get off the Vaporetto at the San Silvestro boat stop. Walk straight until you have to turn right or left, turn left immediately then turn right, keep on walking until you enter Campo Sant'Aponal.
Once in the square there are three streets on you left take the one in the middle (Calle di Mezo) which leads into Campiello dei Meloni. Walk ahead until you see the florists, Biancat, on your right, directly in front to your left is the street Calle della Malvasia at the end of it there is the large iron gate of Palazzo Papadopoli where CNR is located.