Below is a picture I found on the web of the island Amrum at low tide. If you look closely, you can see what looks like rivers, those are the deep currents where the outgoing tide water pull the water into the sea. And you can see where the sand at the north of the island almost touches the next island to the east, the island of Föhr. At low tide you can take a guided hike across the mudflats, which is what we did.
"Die große Wattwanderung"...as our guide called it, "the big mudflat hike," 8 kilometers between the island of Föhr to the island of Amrum.
Our guide was from Amrum, so he kept talking about how we were walking towards "the more beautiful island" (von Föhr nach Amrum, der schöneren Insel entgegen). He was pretty funny, had a lot of "Sprüche," little sayings he repeated over and over, "die große Wattwanderung über den Meeresboden", "Augen auf beim Wattenlauf!" (keep your eyes open on the mudflat hike, rhymes in German) There were two classes of schoolkids along, so a lot of his things were safety reminders. If you don't watch where you are going you can cut your feet on shells or step into deep holes or something.
You are never supposed to do these hikes without a guide, because although the islands look really close at low tide, there are deep areas and unsafe streams of water with strong currents. Crossing a Priel, a deeper area where the outgoing water is pulled out by the tide.
Below: the remains of a shipwreck.
Below: a crab. We saw a bunch of crabs, many birds, little minnows, Wattwürmer, big thick worms that live deep under the sand.
The guide dug a hole and pulled out a Wattwurm for us to see.
Sand as far as you can see!
The little piles of sand everywhere are left from the Wattwürmer, the mudflat worms.