It was an offer by Marriott Moments. I'm only staying at the airport Courtyard for 1 night. It's a 4-1/2 hr. tour of Murano, Murano and Torcello. The tour wasn't expensive but the cost of getting to the dock may be. I wrote the hotel and here's what they told me:
"The shuttle ride after the one at 11.30 is at 12.30 so I would suggest to catch a car taxi for the price of 15€.
You do not need to book a water taxi because usually they are available at the dock of the airport. The price would be around 100-120€."