The fleshy leaves of sea purslane brush our ankles as we pass a weatherboard cottage and walk the path, through the saltings, to the jetty at Alresford Creek, a waterside hamlet tucked away on the edge of the Essex coast near Colchester. An oystercatcher guards the entrance to the broken-down pier, its timbers slowly melting into the mudflats. On the far bank, a lapwing is tumbling above the marshes and a nightingale sings in the scrub. Even on this bright, spring day, it is easy to see why Alresford Creek was chosen for the filming of The Essex Serpent, a new Apple TV series starring Tom Hiddleston and Claire Danes, based on Sarah Perry’s bestselling book. This place feels remote, cut off from the outside world. In 1893, when the story is set, tales of serpents winding their way through the broken boat timbers and sucking teenagers into the ooze must have felt more real to villagers than news of scientific discoveries from distant cities.

Later that day, my mum and I set out from Hythe Quay in Maldon to explore the landscape aboard the Thistle, a Thames barge built in the 1890s. The quayside is a forest of masts, towering above the many barges moored alongside. The rigging hangs like gossamer webs above us. Many of the scenes from The Essex Serpent were filmed on the quay, with locals playing the part of deckhands and dock workers. As the Thistle heads out into the Blackwater Estuary the three small boys sitting beside us go into overdrive. Their mum confesses that they had been reluctant to leave the house that morning, but now they are busy sniffing the sails for a hint of the fish oil sailors used for weatherproofing, and listening with enthusiasm to tales of smugglers and the dead revenue men found floating in Death Creek.

The sky is pebbled with high cloud, skeins of brent geese descend over the mudflats and the terracotta sails of other barges draw the eye upwards in these flatlands. Lunch arrives, a seafood platter of shrimps and smoked salmon pate, made at the nearby Maldon Smokehouse. I drink Wilde Samphire gin with a touch of sea salt and slivers of rosemary floating on top. It is a moment of connection as I get a taste of the land we are sailing past.

We round Osea Island, once a temperance colony set up by brewer’s son Frederick Charrington. He had an epiphany after trying to rescue a woman being beaten by her drunken husband outside one of the family’s pubs. Unfortunately, the locals didn’t quite share his vision and set up a lucrative trade transporting contraband liquor to the inmates who were supposed to be drying out. Nowadays the island is a luxury retreat that still promotes itself as a place to escape a troubled world.

Back on dry land we head to our hotel, the Blue Boar in Maldon, a 600-year-old coaching inn that appears in the Apple TV series. To create a Victorian ambience, the road outside was covered in dirt and packing crates were used to disguise modern street furniture. Inside it is easy to feel transported to another era. Portraits of frock-coated nobles hang on the oak-panelled walls, and suits of armour guard the doorways. The rooms have chandeliers and wardrobes you could travel to Narnia in.

Next morning, we drive through spring-bright lanes to Mersea Island. The beach at Cudmore Grove is busy with families enjoying a moment of sunshine. We are here to search the cliffs for fossils, in imitation of Cora Seaborne, the heroine of Perry’s book. In the story, Seaborne becomes fascinated by tales of a recent earthquake which, it is rumoured, has awakened the Essex Serpent. In fact, an earthquake, one of the most damaging ever recorded in Britain, did rock the Essex coast in 1884 and 300,000-year-old fossils, including the bones of hippopotamus, have been found along these shores.

Sand martins skim our heads as I search the cliffs, picking through the pebbles at their base alongside teenage boys, who are searching, with more hope than luck, for sharks’ teeth. Before long I find a pebble with a dark stain embedded inside. Fossil hunting, it turns out, is easy – far harder to work out what you have found.

“I think it’s a crustacean,” one of the teenagers says, encouragingly.

I think he’s just being kind.

My mum employs a different technique. She lies on the beach, sifting sand through her fingers and crooning fossil poetry in the hope of charming an ammonite into her palm. I don’t blame her; after all, the beach feels almost tropical … trees tumble down to the shore and children walk past with armfuls of oyster shells.

We head off for lunch at the Osea View Cafe Bar at Heybridge Basin, which looks out across the river to Northey Island. My mum plumps for the cream tea with Tiptree strawberry jam, produced for over 150 years at the local factory.

The tide is in as we pull into Tollesbury, our final destination. This boatyard and marina, set amid the saltmarsh, created another atmospheric backdrop for the series. Through workshop doors I spy roof beams hung with tools and weatherbeaten men wiping things down with oily rags. We grab ice creams from the Tollesbury Cafe and walk along the sea wall. White-boarded sail lofts seem set to float away with the incoming tide. Two boys are shrimping from the decks of a cornflower blue houseboat; the warming air is honey scented with hawthorn blossom; gulls wheel and dive for fish. Today the marshes are benign. On a different day, in different light, I can see that this land could hold secrets amid the winding creeks. As we return to town I hear talk of porpoises swimming at the mouth of the Blackwater. Maybe, in this far-flung haven, on the Essex coast, the serpent has returned.
Accommodation at the Blue Boar (doubles from £95pn) and the River Blackwater cruise (from £30pp) were provided by Visit Essex

• The Essex Serpent launches worldwide on Apple TV+ on Friday 13 May