Wadlopen

Twice a day the Wadden Sea empties and a few hundred square kilometres of sand and mud between the mainland and the islands come out of the water, and wadlopen is walking across it - from the Groningen or Friesland dyke to Schiermonnikoog, Ameland or Rottumeroog, or out to a sandbank and back. It takes several hours, the mud is knee to thigh deep in the gullies, there are tidal channels to wade or swim, and the return is timed against a tide that comes in across a flat surface faster than anyone can walk. It is regulated: guides are licensed, groups are required, routes are set, and walking alone is prohibited. Done properly it is one of the genuinely distinctive things you can do in this country, and the Wadden Sea it crosses is on the UNESCO list as the largest unbroken intertidal system in the world.

What's there

• The sea floor on foot - hundreds of square kilometres exposed twice a day.
• Mud to the thigh - the gullies and channels crossed on the route.
• A licensed guide required - groups only, set routes, and walking alone prohibited.
• The UNESCO Wadden Sea - the largest unbroken intertidal system in the world.

When to go

May to September. A day.

Practical notes

Do not do this alone - the tide fills the channels faster than you can walk. Walks are booked, physically demanding, and cancelled for weather or tide. Boots and clothes are ruined.

Nearby

Pieterburen and Lauwersoog are the main start points; the islands are the destinations.