Sub-bottom profiling systems measure various sediment layers that exist below the bottom. A sound source emits a signal downwards into the water and a receiver records the reflected return. Some of the acoustic signal will penetrate the bottom and be reflected when it encounters a change in density such as a pipeline or sediment layers. The system uses this reflected energy to provide information on features beneath the bottom.

Advantages and Limitations:

Sub-bottom profiling systems can be useful for calculating pipe cover or areas of concern, since they provide information about sub-surface sediment structure. The penetration depth depends on the hardness of the overlying layers and the presence of gas deposits, such as methane.