Yesterday I went for a walk along the sea wall at Whitstable. We usually go west but this time tried east, turning round when we reached what is called "The Street" (see iPhone photo above).
It is a nearly straight line of shingle heading almost directly out to sea, as can be seen in this Google Earth picture:
It is such a regular structure that there are some that say it's man-made, maybe created to help harvest the oyster beds as has been done since Roman times.
But according to
Wikipedia it is entirely natural shingle built upon underlying clay. Some more pics
here at geography.org.uk.
As you might expect such a clear navigational hazard is most definitely on the charts:
