The sea bed of the Thames Estuary is known to be an area where water depths can vary considerably due to the mobility of sand banks. In view of this the Port of London Authority undertakes frequent periodic surveys of depths in the recognised buoyed channels and anchorages as described in the PLA Tide Tables and Port Information, and General Directions for Navigation in the Port of London.
Outside the above channels and anchorages, main surveys are carried out less frequently. Mariners are therefore reminded that when navigating outside buoyed channels and designated anchorages they should do so with appropriate caution and not rely on minimum under keel clearances.
