I am not sure what you mean by " regular taxi lines"--- can you clarify?
There are two kinds of transport in Venice, as in elsewhere---public and private. Mthe public transport involves "water buses" known as the vaporetto (serving Venice and the islands but not the airport) and the Alilaguna, which provides transport across the lagoon to and from the airport. Both use designated named docks along the Grand Canal and Round the outside of the island. The Alalaguna also serves a side canal near the train station to get out to the lagoon.
Water taxis can get into the smaller canals and use other designated docks there. There are private and shared water taxis (cheaper) and S far as I know they both use the same docks. A private water taxi from the airport to a Venice hotel is around 100-120€. A shared one is considerably less but you may have to wait for fellow passengers.
Campo Santa Maria Formosa is a long walk from any vaporetto or Alilaguna dock. If you don't mind the price, a water taxi would be a good way to go.