Profile data is collected using a rotating pencil-beam sonar head. The beam can sweep 360º about its axis or sweep from side to side. Data can be gathered from a vertical dam face, across the bottom, under overhangs or other vertical structures. The sonar can be deployed from a small boat and collect bottom data across track. Real time data is displayed on the computer screen and gives the operator visual cues to data quality. If any anomalies are seen in the profiles, the survey can be modified to take them into account.