It is not easy to define the limits of the estuary, although physically the head of Sea Reach, near Canvey Island on the Essex shore is probably the western boundary. The eastern boundary, as suggested in a Hydrological Survey of 1882-9, is a line drawn from North Foreland in Kent via the Kentish Knock lighthouse to Harwich in Essex. It is to here that the typical estuarine sandbanks extend. The estuary has a tidal movement of 4 metres, moving at a speed of 8 miles per hour.
The estuary is one of the largest of 170 such inlets on the coast of Great Britain. It constitutes a major shipping route, with thousands of movements each year including large oil tankers, container ships, bulk carriers and roll-on/roll-off (ro-ro) ferries entering the estuary for the Port of London and the Medway Ports of Sheerness, Chatham and Thamesport.
The Thames sailing barge worked in this area, designed to be suitable for the shallow waters in the smaller ports. One of the largest wind farms in the UK has been developed in the estuary, located 8.5 km north of Herne Bay. The farm contains 30 wind turbines generating a total of 82.4MW of electricity. The much larger London Array of up to 1GW capacity is also planned.
This area has had several proposed sites for the building of a new airport to supplement, or even to replace Heathrow. In the 1960s Maplin Sands was a contender; in 2002 it was to be at Cliffe, Kent. The new airport would be built on a man-made island in the estuary north of Minster-in-Sheppey  There is also some discussion about the need for a Lower Thames Crossing in order to alleviate traffic congestion at Dartford.
The Thames Estuary is part of Thames Gateway, designated as one of the principal development areas in Southern England.
Greater Thames Estuary 
The appellation Greater Thames Estuary applies to the coast and the low-lying lands bordering the estuary itself. These are characterised by the presence of salt marshes, mudflats and open beaches: in particular the North Kent Marshes and the Essex Marshes. Rising sea levels in places may make it necessary to flood some of that land to take the pressure off the defences. Man-made embankments are backed by reclaimed wetland grazing areas; there are many smaller estuaries, including the Rivers Colne, Blackwater and Crouch; and there are small villages concerned with a coastal economy (fishing, boat-building, and yachting). The Isle of Sheppey, Foulness Island and Mersea Island are part of the coastline
Where higher land reaches the coast there are some larger settlements, such as Clacton-on-Sea (to the north in Essex), Herne Bay in Kent, and the Southend-on-Sea area within the narrower part of the estuary
Cultural references 
Joseph Conrad lived in Stanford le Hope close to the Essex marshes. His The Mirror of the Sea (1906) contains a memorable description of the area as seen from the Thames. It is also described in the first pages of Conrad's Heart of Darkness, as both the launching place of England's great ships of exploration and colonization and, in ancient times, the site of colonization of the British Isles by the Roman Empire.
The form of speech of many of the people of the area, principally the accents of those from Kent and Essex, is often known as Estuary English. The term is a euphemism for a milder variety of the "London Accent". The spread of the London Accent extends many hundreds of miles outside London and all of the neighbouring home counties around London have residents who moved from London and brought their London Accent with them. The London Accent or its londonised variants called “Estuary English” can be heard in all of the New Towns, all of the coastal resorts and in the larger regional cities in the southern half of England.
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- "Thames Estuary Passages". the Cruising Almanac. Retrieved 2 March 2013.
- "The Thames Estuary Airport Ltd". Teaco.co.uk. Retrieved 2012-03-18.
- "The Thames Estuary Partnership". Thamesweb.com. 2012-02-07. Retrieved 2012-03-18.
- "English Nature and the Greater Thames Estuary". English-nature.org.uk. Retrieved 2012-03-18.