Sonar technology, specifically underwater imaging, has carved out a place in underwater structural inspection, and one great use of the technology is the identifying and quantifying of scour holes and areas of undermining at bridge piers in waterways that have fast currents. My presentation will go through advantages and limitations of traditional diving methods in such conditions, types of sonar technology often used to scan bridge piers, and tips/tricks for getting optimum images. I will highlight my personal experiences in these types of inspections and conclude with how the inspection data (via diving or sonar) is used for design of effective scour countermeasures.