An experiment to locate objects buried in seafloor sediment by using ultrasonic imaging has been conducted and shows potential for practical application. Attenuation measured in actual seafloor sediment indicated that 15 kHz could be used for detecting objects buried to about 4 m in the seafloor. Tests were conducted using both plane and focused transducers with elements arranged on a concave surface. Imaging of inclined objects by a focused transducer was found to be significantly better than by a plane transducer as long as the object’s gradient was within one‐half the transducer aperture angle. Scaled model tests were carried out at a frequency of 150 kHz and full‐scale tests were performed at 15 kHz. Two display formats were used—one for the vertical plane and the other for the horizontal plane. In the full‐scale test, a cylindrical iron tube and an iron plate were buried in a sand box 4 m long by 3 m wide by 2 m deep. Ultrasonic images were observed on a CRT.