A dredging device (1), comprising: at least one operative arm (2) and dredging means (3) connected to said operative arm (2) and able to be immersed in a liquid. In new and original fashion, the operative arm (2) is so shaped as to generate a hydrostatic buoyancy whose value is just lower than the sum of the weights of the arm and of the dredging means (3), so that the dredging means are immersed deep into the liquid by effect of the difference between the sum of said weights and the hydrostatic buoyancy. A dredging apparatus (50) comprising a self-propelled machine (52) having at least one mechanical arm (51) whereto is connected a dredging device (1).