There is an alluring, unique part of the planet to which we are all granted access twice a day, but which can be lethal to anyone who ventures out into it unprepared. It is a place that can look innocent enough, but is governed by its own rules, and those who haven't done their research could come to a sticky end.
This unusual part of the planet is the intertidal belt. Around most of the UK it's a fickle strip, a matter of a mere few metres wide, but over in the Wadden Sea, along a 450km-long stretch of the north coast of Germany, the water goes out a massive 15km, revealing a huge expanse of tidal flats and leaving even distant islands high and dry. It's like a whole new continent that appears and disappears twice a day.
In these circumstances, a ferry ride to one of those islands in the morning can turn into a walk in the park in the afternoon – in this case the Wadden Sea National Park, recognised by Unesco in 2011 as a World Heritage site for being "one of the last remaining natural large-scale intertidal ecosystems". Something worth seeing.
I chose to do my own walk by the German port of Cuxhaven, where the island of Neuwerk lies 10km offshore. This is one of the top locations for wattwandern, as mudflat hiking is called in Germany. Every year, some 10,000 people either walk out to the island of Neuwerk or ride out over the flats in horse-drawn wagons. Given those numbers, I was expecting to set out with a crowd. But that week's low tides were at antisocial times, meaning a safe crossing necessitated a 5.30am start.
One of the things I'd been warned about was never to deviate from the marked route. In this case, the markers are bits of bush stuck in the mud-sand mix under my (bare) feet. The route has to be remapped every year to make the most of the surface, which is firm enough to support hikers and horse carts, avoiding treacherous goo.
From the shore, the watt looks flat and uninteresting, but once out into it, ooze coming up between my toes, it begins to give up its secrets. I find myself among streams running this way and that, desperately trying to catch up with the departing tide. Some of them turn out to be more than knee deep, and it is these gullies that can ambush the unwary, filling up steadily with returning water while the sea itself still looks some distance away.
About halfway out I'm enjoying the peace, the rarity of the experience of walking on the seabed and the chance to sample an environment yet to be spoiled by human beings. Out in the distance to my left, I know there are seals lying on the sandbanks, while beneath my feet are tiny snails and worm casts. I have to take care to avoid treading on fleeing shrimps and scuttling crabs. To my right are the superstructures of giant ships moving up the Elbe towards Hamburg, without seeming to need water on which to do so.
At this point I pass a couple of safety cages on giant poles, some 6m or so up; apparently they get used on a regular basis by mudflat walkers who misjudge the tide. Coastguard radar can tell whether there's someone in situ. The cages serve as a reminder of the dangers of the flats; in a typical year, a couple of people drown along the Wadden Sea shore. For most of the crossing, Neuwerk doesn't seem to get any closer, but then suddenly, after 90 minutes of walking, I'm arriving at the promised land, striding out of a world of brown on to a big green dimple, a German Maldives, and balm for the eyes.
The island is actually an outpost of Hamburg, for historic shipping reasons, and its signal tower, built in 1367, is therefore Hamburg's oldest building, despite being 130km away. In shape it is a rough-hewn circle, pretty much man made. The island is so low-lying that it had a history of being remade by storms over the centuries, so a ring dyke – a tall, grassed embankment – was built to encircle it and repulse the storms. Within the ring dyke lies a peaceful, pastoral scene of horses and cattle, in a location that gets more sun than Hamburg, and is regularly a couple of degrees warmer than the mainland, partly thanks to the shelter effect of the embankment. Outside the dyke, horses roam and seabirds nest on the salt marshes in huge raucous colonies of sandwich terns, redshanks and black-headed gulls.
Neuwerk has a resident population of just 36, which expands in summer with four hotels, each of which runs its own fleet of horse carts to ferry guests. I stay overnight in the Nige Hus and it quickly becomes clear that the pulse of the place is controlled by the tide. A morning ferry means that lunch gets served in the restaurants and ferry day-trippers can take their time before the return sailing on the next tide. Day-tripper horse carts produce a different impact, coming and going on the same tide, so their passengers have only an hour on the island to eat, drink and enjoy the curative sea air. When the weather is good, it's a frenzy.
As for me, I opt for the ferry back to Cuxhaven the next day, feeling privileged to have walked out across part of the planet where comparatively few dare to tread.
The nearest airport is Bremen, with flights from Stansted, Manchester and Edinburgh on Ryanair (0871 246 0000; ryanair.com). The direct tram from Bremen airport to the main station takes 15 minutes. From there, Cuxhaven is 90 minutes by train.
To walk across the mudflats to Neuwerk, there are routes from Cuxhaven (longer and muddier) or from its resort at Sahlenburg (shorter and firmer, and the route the author chose). If you want to travel across by horse cart, the best operators are the island's hotels, which all offer a cart-ride plus overnight package. Details of ferry crossings with Cassen Eils, walking routes and day-trip horse-cart opportunities are all on the Cassen Eils website www.neuwerkreisen.de. (Download the flyer on the right-hand side.)
Nige Hus (00 49 4721 29 56 1; inselneuwerk.de) has single rooms from €45, including breakfast.