Water taxis, or normal boats.
I would go by train. Trains in Europe run on time and are efficient. There are also plenty of buses. They too are good.
There is no train station linking either Venice San Marco or Venice/Treviso airports to the city of Venice. From Venice San Marco airport you can take a bus (water bus) to the city or you can take a...
537 kilometres (333.68 miles)
Marco Polo (VCE)
Marco Polo International Airport