The nature of seabed is important if the marine current turbine is to be mounted on a monopile or fixed using moorings. Coastal locations with high tidal activity tend to have scoured seabed with exposed rock, which is ideal. However, some sites may have sediment lying ontop of rock such as sand, mud, gravel or shells. Such layers of sediment will not have a major effect, as developers would simply drill slightly deeper.
Admiralty charts mark the nature of the seabed. However, this information is only to enable sailors to make the correct decisions when anchoring vessels, therefore a more detailed geological study or survey would obviously be required by developers.