A detection system to check the position of a pipeline in a bed of a body of water and extending along a predetermined route; the system comprising a device, which is configured to be moved in a moving direction and along the predetermined route and comprises a support, which mainly extends transversely to the moving direction, a quantity of acoustic wave sources, which are mounted on the support and are configured to transmit acoustic waves through the body of water and the bed of the body of water, and a quantity of acoustic wave receivers, which are located along the support and are configured to receive reflected acoustic waves and emit reception signals related to the reflected acoustic waves; and a processing unit comprising an acquisition unit, which is configured to receive, from the outside, at least one datum selected within a group of known or expected data comprising: the known value of the cross-section of the pipeline, an expected value of the trenching height of the pipeline, the known shape of the pipeline, the expected bathymetric profile of the bed of the body of water, and an expected value of the position of the pipeline; the processing unit being configured to calculate a parameter related to the position of the pipeline in the bed of the body of water on the basis of the reception signals and of said at least one datum selected within the group of data.