This dataset consists of Images produced from a Seapix-R multibeam echosounder (MBES) pointed at a fish farming cage. The MBES was attached outside the cage on a mounting bracket with a 45 deg downwards tilt, such that most of the cage was within the vertical beamforming capability of the system, with the exception of a small cake-shaped section near the net, 1.5 meters high, extending 5.5 meters into the cage