Wilhelmshaven is a working North Sea port with a stronger maritime identity than most German coastal towns. It was founded as Prussia's naval harbour in the 19th century, and the German Navy is still part of the city's character, but the visitor appeal is now concentrated around the harbour, the museums, and the edge of the Wadden Sea.
The best reason to stop is the maritime mile around the Sudstrand. The German Naval Museum lets you walk through Cold War warships, while the Kaiser Wilhelm Bridge swings open above the harbour basin like a piece of early industrial theatre. A short walk away, the Wadden Sea Visitor Centre explains the tidal flats that make this coast a UNESCO World Heritage landscape.
Wilhelmshaven is not a postcard old town. Much of it is practical, rebuilt, and port-like. That honesty is part of the appeal: you come for ships, sea air, big harbour engineering, and easy access to the Lower Saxon Wadden Sea rather than half-timbered streets.