I think that in order to appreciate the Wadden Sea you have to go on a mudflat hike. Living in Hamburg, I have been to several ones, and I always find this weird ecosystem fascinating. Coming from Hamburg you can reach the Northern Sea at Dünen/Cuxhaven in Lower Saxony or at Friedrichskoog/Büsum/Sankt Peter in Schleswig Holstein. I have been to mudflat hikes at all these points and, surprisingly enough, the landscape and the nature of the hike differ considerably. One of the reasons is a feature of the Wadden Sea called tidal creeks (Priele in German). These are streams which appear during low water and can be very strong. Their route remains steady. If you go hiking next to such a tidal creek you cannot normally cross it. This affects the distance you can reach from the beach. This is why a mudflat walk from Büsum, for example, cannot take you to the deep sea. The terrain is also different, with mud of various degrees of density. Finally, in some hikes you can reach areas in which you can observe seals. I personally preferred Cuxhaven as a point of departure. Hikes can take from 1 hour up to 6 hours. Make sure to either join a tour or take the necessary precautions as mudflat hikes can be dangerous.