From Marco Polo Airport to San Marco-San Zaccaria stops

There are many threads here discussing transportation options in Venice
A search will bring them up- look for “ Aussies’s” helpful posts

Your options are
Water taxi - shared or private
Alilaguna boat
Bus or land taxi to P Roma then vaporetto

Most hotels in Venice will have directions “how to reach us“ on their website

You've got 4 options:

Most expensive and easiest is to take a water taxi directly to your accommodations. No need to book in advance, just go to the water taxi desk at the airport.

Next most expensive and almost as easy is a shared water taxi to the vaporetto stop. Again, just go to the water taxi desk and ask for a shuttle or shared taxi.

The easier cheap option is Alilaguna from the airport. Buy your ticket at the airport and ask the dock worker for the next boat to San Marco.

The more complicated cheap option is to take a land bus (ACTV or ATVO) to Piazzale Roma, then a vaporetto to San Marco. ACTV offer combo tickets for the bus and vaporetto but I think they just use a plain city bus, while ATVO use coach buses.

The ACTV No 5 bus is a low floor articulated bus with seats on the side like a subway car.