Abstract: A vessel of generally conventional design is provided with a hydrographic survey apparatus in which the transducer of the survey apparatus is mounted on a boom swingable about a substantially horizontal axis between a deployed and stowed position. The boom is located in a slot aligned in a vertical plane along the boat's centerline and extends downward from the boat's top deck. The boom is mounted at one end near the bow of the boat by attachment to a drive shaft extending beam-wise or transversely across the slot. The drive shaft is operated by a hydraulic rotary actuator. The transducer is mounted on the free end of the boom and is swingable about the drive shaft into and out of the water. The transducer is thus selectively movable from a stowed position to a deployed position in front of the vessel where it is placed in still non-turbulent water, i.e.; water that is free from mechanical vibration and noise of the survey boat and aquatic turbulence from the hull.