An acoustic antenna element for receiving and/or emitting low-frequency underwater waves comprises an acoustic panel formed by at least one acoustic pick-up enclosed in a flexible jacket, the acoustic panel being generally rectangular and being mounted against a curved support by a mounting device including a clamping device comprising at least two flanges the ends of which are mounted on the support, the respective flanges comprising at least one tie between the two ends thereof, and the clamping device capable of adjusting the tension in the ties between the two respective ends thereof, the flanges being arranged so that the support is bent between the two respective ends of the ties and so that the panel is clamped against the support by the ties when they are under tension.