I found Cristiano, who sang O Sole Mio for me! Fascinating ride. the price is 80 euros for 30 min. It is standard fare decided by the guild. Read more on my blog "A mind of my own."
A little bit disappointed with this .... the guide never spoke to us. We were seven on the gongola and it was somewhat precarious ... 6 tourists and the guide. It could have been much more enjoyable if he had interacted with us!