Kentish Knock

The Kentish Knock is a long shoal (bank, shallows) in the North Sea east of Essex, England. It is the most easterly of those of the Thames Estuary and its core, which is shallower than 18 ft, extends 6 mi. Thus it is a major hazard to deep-draught navigation. It is exactly 28 mi due east of Foulness Point, Essex and is centred about 15 mi NNE of North Foreland, Kent – both are extreme points of those counties.

Shape
It is about equidistant between, on the one hand, the south-west North Sea tidal amphidromic point (place of negligible tides); and splayed on the other the narrowest point and endpoint of the English Channel (the Strait of Dover) (southeast) and heart of the Tideway (southwest) which have by contrast high tidal range. It is thus among a succession of banks which are aligned NNE to SSW but turn towards the estuary narrowing further west. In line with the erosion and deposition from each such regular tide, its north – its steepest, narrowest part – veers slightly more towards north-south alignment than its south.

Ecology
Made of sand and gravel, it hosts hermit crabs, sand goby, rays and catsharks. In rare species it has visiting red-throated divers. Channels are believed to have been caused by glacial floodwaters many millennia ago. Since 2012, The Wildlife Trusts have been campaigning for recognition of a 37 sq. mi. (96 km2) section of the Knock, known as Kentish Knock East, as a Marine Conservation Zone.

Scope and soundings
To explain the numbers on the inset map a depth of 11 is a formula of six feet (i.e. one fathom) and 1 foot. It is $1 1/6$ fathoms. Some of Kentish Knock is, or was, at chart datum "01". At just one foot in depth it will have become exposed at the ebb phase of most extreme, spring tides.