What is the cheapest way to get from the San Marco Airport to San Marco Square?

Cheapest would be using the No 5 bus to Piazzale Roma, then vaporetto ticket (to San Marco or anywhere else you want to go), costing 14 EUR each way. If you plan on staying a few days and want a vaporetto pass while you are there, the bus adder is 6 EUR each way.

The cheapest method will probably be the Bus to Piazzale Roma that Sam mentioned and then Vaporetto to Piazza San Marco. The easiest method will likely be the Alilaguna direct from the airport station to Piazza San Marco.

Even cheaper is bus number 5 as above, cross the Grand Canal by the glass bridge or stay on that side until the Rialto bridge, and the whole walk is scenic and reasonably quick if you don't mind a few bridges.

Bus and walk is cheapest.

Where is San Marco airport?

I doubt very much that Marco Polo has been beatified without I heard about it

lol

Oops, yes, the Marco Polo airport...I was posting late last night! I appreciate all the information that has been shared. Does anyone have experience with Aliliguna when purchasing just their E27 round trip on the red line? The more research I'm doing the more I see very mixed reviews. The positive reviews seem to be from people who used them and paid for the very expensive private taxis service and not for the communal boat ride.

We just took a taxi. It was cheaper than two tickets on the vaporetto, it was fast and we didn't have to wait.
You're on vacation and it's not always best to be "cheap."

I thought that the Alilaguna was a great idea until I took their boat one year. I had seen Lola's advice here - I think it was Lola so I don't offend somebody else if it wasn't - and ignored it.

My take -

The water taxis to Venice from the hotel are very expensive and the walk to them at the airport is no fun with luggage.

The Alilaguna docks are even further to walk at the airport.

The land taxi and the land bus (number 5) both pick up immediately outside the baggage collection hall, and on them you can be most of the way to Venice before your walk to the Alilaguna is finished.

The land bus is the cheapest alternative of the lot.

The Alilaguna boats are motoscafi shaped, narrow, and down several steps into the cabin, leaving your luggage up on deck with the crew - and everybody else's. There are either no chair-type seats in the Alilaguna or it is all benches along the walls, my memory is faulty, but I am sure that we were on benches looking across the cabin at benches looking back at us. There are small sideways facing windows high up in the cabin, and two windows, like small windscreens, facing forward. All the windows were hard to see through because the cabin is steamy inside and condensation forms on all the windows on the inside and they are caked with salt on the outside. You can sort of see boats passing you, but only if they are close and you see mostly the tops. I know Venice well having visited it at least once a year for many years, but on the Alilaguna I found it hard to work out where I was as we forged ahead. They are also not fast. The boat may not leave the airport when it is full, there are various reasons. Each boat makes several stops and if yours is not the first you will have people clambering to get off and claim their luggage and get onto the dock. Sometimes this is fast, sometimes not.

Whether you prefer it is up to you of course, but the title of your question is asking for the cheapest way.

I happen to think that the cheapest is actually the best in this scenario.

Nigel---that description! Oh my goodness I felt as if I was there with you. It is those little details which allow us to imagine the everyday realities. Thank you!

SuzieeQQ

Thank you so much for your description and expert advice. It's very hard for those of us who have never been there.

Nigel: Yes, thank you for that very descriptive account! I had been weighing the same options, bus/vaporetto vs. Alilaguna, with the expensive water taxi not in the running. Your detailed description has convinced me to take Alilaguna out of the running as well. Very, very helpful. Just the kind of information I look for on this forum.

It may well have been a post of mine that influenced Nigel. While I used to advocate for the Alilaguna---on the oft-stated sentiment that "Venice is best approached from the sea", after recent experiences I no longer do.

The first time we rode the Alilaguna was in 2003, on our honeymoon trip. We arrived in early evening, and walked down to the dock to wait for the next boat. It was nearly dark by the time we boarded. It was a larger boat than the one described by Nigel---more like one of the vaporetti, but with rows of bare-bones seats in the back area. It was cold, and the windows were crusted with salt spray so we could not see out. The one redeeming feature of the trip was that the landing dock on Zattere was very close to our hotel.

On two subsequent trips I arranged our itinerary so we would arrive in Venice by car or train, avoiding the airport. But in 2013 we did fly out of Marco Polo, and the trip was exactly as Nigel described: the small boat with seats around the wall, luggage piled here and there, including the space at our feet so we were wedged in. One could not see a thing out the windows. I tried to stand for a better view out the hatch, and was ordered to sit down. It was a good thing we boarded at Rialto, as the boat filled up and at subsequent stops they left people standing on the dock as there was no room.

After that I no longer recommend the Alilaguna. The bus from the airport to Piazzale Roma is fast and easy, and boarding the vaporetto there gives you a significant advantage over the hordes who come aboard at Ferrovia, the next stop.

Just left Venice yesterday and we used a water taxi from the hotel to the airport. The airport has finished construction from the dock to the terminal and it is fantastic. Walking escalators all the way. Our airports in the USA are such a mess compared to Europe's.
We arrived in Venice by train and also used a water taxi that cost $50 which took us to our hotel (Westin). We booked it on Viator and ended up being the only couple on it all the way down the grand canal.
I mention this only because we saw so many people with their luggage struggling to get on/off the public water taxi's from or to their hotels along the very crowded areas where the stops are.. They were miserable. The San Marcos stop can be chaotic
Pay the extra dollar for the easiest mode of transport, it will save so much stress believe me!.

Safe travels!