There is something faintly disobedient about seeing a seal in London.
A seal belongs, surely, to postcard coasts and salt-bitten harbours, to places where people own binoculars on purpose. Not here. Not in a city of Uber Boats, glass towers and wet paving slabs. And yet the Thames, with its long memory and murky glamour, keeps producing them: glossy heads in the water, dark eyes above the chop, a small pagan miracle between the concrete.
The great surprise is not that seals occasionally wander into London. It is that they are now a recognised, thriving part of the Thames ecosystem. The Zoological Society of London’s latest figures estimate around 2,988 grey seals and 599 harbour seals in the Greater Thames Estuary, a remarkable marker of how far the river has come from its industrial nadir.
Of course the Thames estuary stretches all the way down to Essex / Kent and the North Sea, but even so London has seals. Quite a lot of them, in fact. The city just likes to reveal its enchantments in an offhand way.
A river once written off
The Thames was once declared “biologically dead” in central London, a phrase so bleak it sounds like a Victorian diagnosis. But over the past decades the river has staged one of the capital’s quieter comebacks. Improved regulation, cleaner water and sustained conservation work have helped restore an ecosystem that now supports fish, birds, eels, porpoises and, increasingly visibly, seals. ZSL’s State of the Thames report, published on 19 January 2026, presents them as one of the river’s most charismatic success stories, while also warning that pollution and warming waters still threaten that recovery.
That is the strange poetry of the modern Thames. It is still working, tidal, commercial, difficult, brown as builder’s tea in places — and alive in ways that would once have seemed improbable.
Which seals are in the Thames?
Two species dominate the story: grey seals and harbour seals.
Grey seals are the larger, rangier creatures, with the long dog-like profile that makes them look as though they know something compromising about the government. Harbour seals are smaller, rounder-faced and often described as more catlike in expression, which feels right for London: even its marine mammals come in subtle personality types. ZSL says both species are now found throughout the estuary and river, including central London.
Public sightings have been logged since 2004, and they show just how far inland these animals are willing to travel. Seals are “frequently sighted all the way up to Richmond”, which means that a creature many people associate with lonely sandbanks can, under the right conditions, appear startlingly close to rowers, runners and people carrying oat flat whites.
Where are London’s seal hotspots?
If you want the headline answer, it is this: Canary Wharf.
ZSL identified Canary Wharf as London’s seal-watching hotspot, with more sightings reported there than anywhere else along the Thames Estuary in one major long-term survey. That same survey also found plenty of records in central London, especially between the Houses of Parliament and the O2 in Greenwich, as well as around Hammersmith.
More recent Thames mapping continues to show sightings around Richmond, Hammersmith, the Tower of London, Greenwich and Thamesmead. In other words, seals are not merely estuary creatures glimpsed on the city’s far eastern edge. They are part of London’s tidal drama, turning up in places where office workers, tourists and joggers least expect them.
This is part of their appeal. A seal in Norfolk is lovely. A seal near a luxury development, watched by a man eating Pret at speed, is something richer: a reminder that London is never fully domesticated.
Why are they here?
Because the river, for all its bruised history, can feed them.
Seals are top predators. Their presence suggests a food web robust enough to sustain them, and ZSL describes them as important apex species in the estuarine environment. They haul out on sandbanks and mudflats in the outer estuary, but they also travel the tidal system, following opportunities and navigating a landscape that is both natural and aggressively urban.
There is also a seasonal rhythm to their appearances. The Port of London Authority notes that common harbour seals are most commonly seen between June and August, with August being a key moulting period when they spend more time hauled out on sandbanks. That makes summer one of the better times to keep your eyes on the river, especially downstream.
Still, this is the Thames, not a safari park. There are no guarantees. Part of the thrill is that you are looking into a river that often appears opaque and ordinary, and then suddenly it blinks back.
How to spot one
The best method is gloriously low-tech: walk, pause, scan, repeat.
Riverside stretches in Docklands, Greenwich and further east offer some of the strongest chances, while upriver sightings do happen, particularly on the tidal reaches. Low tide can improve your odds because seals may be easier to spot resting or surfacing in calmer, shallower-looking sections.
But there is a behavioural trick here too. To notice seals in London, you have to resist the city’s normal visual tempo. Most people look through the Thames on their way to something else. Seal-spotting requires a different gaze — slower, more suspicious, willing to believe that the river is withholding things from you.
Which, to be fair, it is.
What should you do if you see one?
Admire it, then leave it alone.
Both ZSL and the Port of London Authority advise people not to approach seals, not to feed them, and to keep dogs under control. Resting seals can look stranded or sleepy when they are in fact simply hauled out, and disturbing them can cause stress or push them back into the water before they are ready. The PLA also warns that the tidal Thames is a difficult environment where water levels rise quickly.
In other words, the correct London response to a seal is not: selfie, sprint, Labrador chaos.
It is to give the animal the courtesy of distance.
The Thames, re-enchanted
What seals really offer London is not just biodiversity, but perspective.
They make the city feel older and less obedient to itself. They puncture the fantasy that every inch of the capital has been fully monetised, mapped and explained. Here, in the same river that carries clippers, sewage history, reflected skyscrapers and centuries of trade, is a sleek wild mammal surfacing as if all of this were entirely normal.
Perhaps it is.
Perhaps the real oddity is that we ever expected the Thames to be only a backdrop — a strip of scenery for joggers and property brochures. The seals suggest otherwise. They remind us that the river is not decorative. It is alive, tidal, moody and only partly civilised.
Which may be why London loves it so much.
And why, when a seal appears near Canary Wharf or Greenwich or Richmond, the city briefly looks caught off guard — as though nature has slipped in through a side entrance, perfectly at ease, and taken its seat.