In order to simulate the detection of underwater gas seepage by acoustic sensors, a controlled experiment was carried in the Paranoá Lake (Brasilia, Brazil) to verify whether multibeam echo-sounders are able to detect and characterize bubbles both at their generation point on the lake-floor and along the water column. The experiment involved the acquisition of acoustic data from a purpose-built submerged target, with and without the presence of gas bubbles. The target was built using a 1×2 meter acrylic plate, mounted on an iron structure, with an air injection system for bubble formation. The air injection system was built using 0.5-inch tubes, which were drilled for air venting, and attached to the bottom of the acrylic plates. Such an arrangement allowed for simulating the presence of gas at the lake-floor. Two vessels were used for the data acquisition, the first equipped with a multibeam sonar system, and the second with an air injection system, including an air compressor powered by a generator. The experiment was carried out at two sites at Paranoá Lake, with different water depths (6 and 13 meters). The study site was chosen due to its proximity to the laboratory facilities and favorable conditions for target implantation. During the experiment, bottom disaggregated sediments and mud buried the controlled target (which is only 4cm thick) in the bottom of the lake, making it difficult to discriminate its position based on bathymetric data. Nevertheless, the results allowed us to observe the bubbles both at their generation point on the lake-floor and along the water column, on a 3D perspective. At the shallower site, the bubbles seemed more densely concentrated near the target, while at the deepest location, they were more spread out around the target area, which can be explained by the increase of ambient pressure with depth which should reduce both bubble size and density.