Flat-bottom boat across the Wadden Sea — drying out on a sandbank

There is a manoeuvre in Dutch sailing with no real equivalent elsewhere: droogvallen, deliberately running your boat aground on a sandbank and waiting for the tide to leave you high and dry. A flat-bottomed boat — a traditional tjalk or klipper, no keel to speak of — settles upright on the sand as the water drains away, and for a few hours you step down onto a seabed that exists only twice a day. All around, the Wadden Sea empties to a shining plain of sand and mud and winding channels, and the horizon fills with wading birds working the flats. The Wadden is a UNESCO World Heritage site, the largest unbroken system of intertidal sand and mud flats on earth, stretching from the Netherlands up the German and Danish coasts. You sail out from a harbour such as Harlingen, Enkhuizen or Makkum aboard a chartered flat-bottom, often a century old, its leeboards and gaff rig unchanged in principle for generations. The skipper reads the tides and the shifting channels — a skill that takes years — and picks the bank where you will spend the low water. When the boat settles you can climb down and walk, boots sinking, out across the drained seabed; some trips join a guided wadlopen, the Dutch discipline of walking the flats. Then the tide turns, the channels refill, the birds lift, and the boat floats itself off as though nothing had happened. It is modest in price and grand in feeling, and unrepeatable by design — a landscape that appears and vanishes with the water. As one of the two Dutch anchors on the list, it is also the easiest to reach: a short trip, close to home, that most people have sailed past their whole lives without once stopping to stand on it.