The River Thames is a relatively shallow river overall, with its deepest surveyed sections reaching about 20 metres (around 66 feet), mainly in the central and lower tidal stretches through London and towards the estuary. Much of the river is significantly shallower than this, especially upstream.

Typical depth overview

  • The deepest parts of the Thames are estimated to be around 20 metres (66 feet), particularly in the tidal sections near central London and toward the estuary, where the channel is maintained for large vessels.
  • In many middle reaches, a more typical depth is roughly 4–5 metres (13–16 feet), depending on the local channel shape and river management.
  • Upstream near the source in the Cotswolds, the river can be extremely shallow, sometimes around 0.5 metres (1.6 feet) in places.

Depth in London

  • Through central London, the Thames is a tidal river and its depth changes with the tide, dredging, and river engineering.
  • Average depths in central London are often quoted in the range of about 5–9 metres (16–30 feet), though local pockets can be deeper where navigation channels are cut and maintained.

Tidal effects on depth

  • In the tidal Thames, high and low tide can change the water level by several metres, so the effective depth at a given spot can vary a lot over a single day.
  • In some central London locations, depth at high tide can reach well over 10 metres because the tidal range stacks on top of the underlying riverbed depth.

Upstream vs estuary

  • Above Teddington Lock, where the Thames becomes non‑tidal, average depths are much smaller, often around 2 metres (about 6.5 feet) in many reaches, with deeper pools near locks and bends.
  • As the river widens into the Thames Estuary, depths in navigational channels generally stay in a band of roughly 8–20 metres (26–66 feet) to support commercial shipping to and from the Port of London.

TL;DR: The Thames is not uniformly deep: in places it is barely half a metre near its source, usually a few metres deep along much of its course, and up to about 20 metres deep in its deepest tidal sections near and below London.

Information gathered from public forums or data available on the internet and portrayed here.