A ferry is a big ship, that is a type of transportation, usually a boat or ship, used to carry people and sometimes their cars over a body of water. Ferries are also importand to the public transportation systems of many cities and islands that are along the waterside. Allowing straight transportation between points at a total cost that is less than the total cost of bridges and tunnels.
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public transport
ferry

                                                                                                                            
a ferry in Puget Sound
                                                                                                                                  ferry docking