Water Taxi or other transportation to Venice airport

Hard to say without knowing what "best" means to you. Is "best" cheapest, fastest, most scenic, fewest bridges, easiest?

Or not knowing how many in the party, how early in the morning the flight is, how much luggage, walking difficulties if any etc.

Especially not knowing where your hotel / airbnb / guesthouse / vrbo or cruise ship is.

Depending on the above you could choose from:

Vaporetto or walk to P Roma and catch a land bus or land taxi.

Vaporetto or walk to an Alilaguna stop and Alilaguna to the airport dock and walk.

Shared water taxi to the airport dock and walk.

Private water taxi to the airport dock and walk.

Private launch to the airport dock and be met by a private car and taken to departure lounge.

Above are in relatively increasing price.

To put it in perspective, the first two are about 14 to 15 EUR per person (using the bus, not the land taxi)
The private water taxi is about 100 EUR, but it holds up to 5 without surcharge, and up to 5 more at 10 EUR per person.

What time is your flight? Where is your hotel? How many people and how much luggage? Any mobility issues? Budget? Those answers may help narrow down your choices.

Our Delta flight departs from the airport in Venice on Saturday, September 17th at 1:25pm.
Our Airbnb is in/near St. Mark's Square.
No mobility issues.
My husband and I each have a carry-on and I have a shoulder bag.
No budget issues. Willing to pay the 100Euro total if it's worth the experience.

I used these guys twice and liked them. https://www.motoscafivenezia.it/ You reserve ahead of time if you want.

It will cost you around 100 Euro or so. But, the trip is worth it. I think everyone should do this once. We went from San Marco to the airport for an afternoon flight. The route is interesting and you get good views of Venice and the other islands as well as the airport. I recommend it. Water taxis can move fast across the laguna.

Enjoy it.

Ask your hotel for a recommendation. We had a similar departing flight schedule (around 1:00 pm), staying near the Rialto, and we were advised by our hotel to take a Vaporetto to P Roma then catch the bus from there that takes you directly to the airport. Worked perfectly and was by far the most cost-effective option for us.

I believe they are asking for the best experience, not the cheapest. While the vaporetto + bus is a perfectly good option, suitable for most people and very cost-effective, it does not compare to the experience of riding in a water taxi. In many trips to Venice, we have only done the water taxi once (5 of us together from Piazzale Roma so not too bad €€€- wise). We only covered the Grand Canal but it was so great. And going across the Lagoon would be nice too----much better views than you get from the Alilaguna.

I could not get the motoscafi website to work to see if it comes in under €100 with advance booking, but you can check it yourself.

I also recommend https://www.motoscafivenezia.it/eng/
There are also other companies that offer the service, but some have had them never show up or show up late. If your lodging has its own dock they pick you up right there. Reliable and friendly. No tip expected. I used paypal and had no problems with my credit card being expected. 5% discount if you book both ways. Just checked their website and it is operational. Enjoy!