An estuary is where a river meets the sea, and most coastal visitors treat it as an obstacle to be crossed on the way to somewhere with waves.
I spent a week based on one by accident, because it was the only accommodation available, and I have gone back deliberately three times since.
Why they are more alive than open coast
Estuaries are among the most biologically productive environments anywhere, and the reason is straightforward.
Rivers bring nutrients from the land. The mixing of fresh and salt water, plus the shallow depth and the twice-daily exposure of mudflats, creates conditions in which enormous quantities of small organisms live.
That supports everything above it. Estuaries are where you see birds in numbers that open coastline does not produce — waders feeding on falling tides, wildfowl, and in the right season migration on a scale that is genuinely startling.
They are also nurseries for fish, which is why the fishing communities historically sat at estuary mouths rather than on the open shore.
The tide does more here
Everything I have written elsewhere about tides applies double in an estuary.
The water moves further horizontally, because the land is flat. A channel that a boat can navigate at high water becomes a stream between mudbanks at low.
The current in the channel can be very strong, because a large volume of water is moving through a narrow gap twice a day. Estuary currents are frequently faster than anything on the open coast nearby.
And the timing is offset from the open sea, sometimes by an hour or more, because it takes time for the water to fill and empty. Using the tide table for the nearest coastal town rather than for the estuary itself is a genuine error here.
The caveat, which is serious
Estuarine mud is dangerous and it does not look it.
Soft mud can be deep enough to trap somebody, and the combination of being stuck and a rising tide is the specific situation that produces rescues and occasionally worse.
The mud that looks firm from the bank is frequently not. Local knowledge about which areas are safe is real knowledge and worth respecting entirely.
The practical rule is not to walk on mudflats at all unless you are with somebody who genuinely knows the area, and never on a rising tide.
Channels are the other hazard. A channel that appears shallow can be deep and fast, and crossing one that seems trivial at low water is how people get into difficulty.
What there is to do
Birdwatching, obviously, and it is worth doing even for people with no interest in birds, because the numbers are the spectacle rather than the identification.
The best viewing is generally a couple of hours either side of low water, when the feeding areas are exposed and the birds are concentrated, and again on a rising tide as they are pushed toward the shore.
Walking, on the paths and sea walls that almost always run along estuaries, which give long flat routes with continuously changing views.
Boats. Estuaries are where small boat activity concentrates, and a trip up an estuary on a rising tide is one of the better cheap excursions available on any coast.
And the towns, which tend to be older and more substantial than open coast villages, because estuaries were where ports could exist.
The food is frequently better
An observation across several estuaries and I think there is a reason.
Shellfish, particularly. Oysters, mussels, cockles and clams are estuarine, and where a fishery still operates the product is landed within minutes of where it is sold.
The towns also tend to have a resident population rather than a seasonal one, which supports restaurants that operate year round and cook for people who will come back.
The one caution is water quality, which affects shellfish directly. Estuaries receive whatever the river carries, and commercial harvesting areas are classified and monitored for exactly this reason. Buying from a proper source rather than gathering yourself is the sensible position unless you know the local situation well.
What to check before going
Whether there is a path along it, which most have and some do not.
What the tide does, specifically for that estuary rather than the coast.
Whether there is a hide or a reserve, which most significant estuaries have and which is the easiest way in for anybody new to this.
And whether the town on it is a working one, since the estuary towns that have kept a function are considerably more pleasant to stay in than the ones that have not.
The seasons are more distinct here
Unlike an open beach, which is broadly the same thing all year with different weather, an estuary changes character completely between seasons.
Autumn and winter bring migrating and overwintering birds in numbers that summer does not, which means the traditional off-season is the peak season for the main attraction.
Spring brings breeding activity and the return migration. Summer is the quietest period biologically and the busiest for boats.
Which inverts the usual coastal calendar entirely, and means an estuary is a genuine answer to the question of where to go on a coast in January.
The light
One more thing worth mentioning. Wet mud and shallow water at low sun produce reflections that no other landscape offers, and estuaries at dawn and dusk are the reason a lot of landscape photographers spend their time standing in cold places.