Virtually all larger boats have constant-speed, variable-pitch propellors in the same way as a turboprop or complex single aircraft. In the same way as these aircraft, they can go backwards (inefficiently) with reverse pitch.
Some boats DO have bow thrusters. They are a small prop mounted at the front of the keel crossways - pushing to port or starboard. They are used when manouvering in or out of harbour, allowing the boat to turn without moving forwards or backwards.