Sailing the Wadden Sea: tidal inlets, channels, drying out and tidal windows

In the Wadden Sea between Den Helder and Esbjerg you sail by the tide. Channels, watersheds and sluice harbours are usually passable only in a window around high water. Pass tidal inlets preferably on the flood, and never in a strong onshore wind against the ebb. The shallowest point on your route always decides.

What is the Wadden Sea?

The Wadden Sea is the shallow coastal strip of the North Sea behind the West, East and North Frisian Islands, large parts of which dry out at low water. In Germany and Denmark it is a national park, in the Netherlands a protected area, and as a whole a UNESCO World Heritage Site.

The water rises and falls twice a day, with around 12 hours and 25 minutes from one high water to the next. The tidal range at Cuxhaven is around 3 m. How the tide works is explained in the guide Tides and tidal streams.

What is a tidal inlet and what is a channel?

A tidal inlet (Seegatt) is the deep gap between two islands through which water flows into the Wadden on the flood and out again on the ebb. The channels (Priele) are the branching gullies in the Wadden behind it, which get shallower and shallower towards the coast.

Tidal inlets and channels shift with every storm, and buoys are moved. So take the current chart and the Notices to Mariners with you.

When can I safely pass through a tidal inlet?

Most safely on the flood in moderate winds: the flood stream carries you in, and wind and stream run in the same direction. In a strong onshore wind against the ebb stream the sea breaks on the bar, and then you stay in harbour.

Wind against tide builds a short, steep sea in a tidal inlet even in moderate winds. On the North Sea coast, onshore means winds from west to north. If you want to go out, you usually take the first of the ebb, as long as the wind is not against it. Also watch for swell after a gale: it can still break long after the wind has eased. More in the guide Sea state and waves.

How do I work out a tidal window for a channel and a sluice harbour?

The depth of water is the charted depth at the shallowest point plus the height of tide above chart datum (CD). If that is enough for your draught plus a reserve, the window is open; usually it lies either side of high water.

If the shallowest point dries, the chart gives its drying height above chart datum. Then you calculate like this:

Two things shift the window. At neaps high water does not rise as far, and an offshore wind pushes water out of the German Bight so that the level stays below the prediction. So plan to cross the shallowest point on a rising tide: if you run aground, the flood will float you off again.

Sluice harbours such as Bensersiel or Neuharlingersiel can only be reached in a window around high water. Many island harbours also dry out completely or in part; the pilot book tells you whether your berth keeps water.

Can I dry out in the Wadden Sea?

Yes, with the right boat: bilge-keelers, lifting-keel boats, centreboarders and keelboats with legs can dry out on firm, level sand. A keelboat without legs falls over on its side and does not belong on the flats.

Pick a spot outside the channel and outside protected areas, free of stones and mud, and put the anchor out. Check beforehand when the water will return, and be ready when the boat floats. Do not walk far across the flats: channels fill with the flood faster than you think, and fog often comes in suddenly.

Which rules apply in the Wadden Sea National Park?

In the German national parks there are navigation regulations: Zone I is generally closed, and seal and bird sanctuaries are marked on the chart and in some cases closed seasonally. In the Netherlands the temporarily closed areas are shown on the Waddenkaart, and in Denmark wildlife reserves with bans on navigation and landing apply.

Keep your distance from seals on the sandbanks, and only dry out outside closed areas. The rules for each country are on the pages Germany, Netherlands and Denmark.

Which harbours lie in the Wadden Sea?

From west to east, these include:

How does Sailseer help in the Wadden Sea?

Sailseer builds the tide into your planning. You lay out a route on the map, for example from Norderney to Bensersiel, and see when there is enough water over the shallowest point.

• Tide gauges: the BSH tide gauges on the North Sea with the next high and low waters, astronomical and with wind-driven surge.
• Tidal curve at every point from the Copernicus Marine ocean model, with high water, low water, tidal range and height of tide above an estimated chart datum, plus spring and neap times.
• Channel depths from EMODnet: the route runs via the fairway buoys of the tidal inlets and through the channels, and the shallowest point of every section is known. From this Sailseer calculates the time window for tidal inlet and sluice harbour and, in the weather analysis, waits until there is enough water.
• Tidal stream in speed over ground: if the foul stream is stronger than your boat, the plan waits for the turn of the tide. Sailseer flags wind against tide from 0.8 kn of stream and 12 kn of wind.
• Multi-day trip: “Check the tidal window at each day's destination” takes the shallowest bar in the last 10 nm.
• Chart: in Germany the content of the BSH ENCs, in the Netherlands Rijkswaterstaat's inland ENCs including the Wadden Sea.
• Weather: DWD warnings for the German Bight and the coast, wind measurements on Borkum, Norderney, Helgoland, Sylt and at other stations.

For navigation, the official chart, the tide tables and the Notices to Mariners apply. Sailseer is not for navigation.