Althäuser See is a freshwater lake in Kronau with a local dive center right next to the water, multiple purpose-built entry points, and a controlled setup for lake diving. It is a good place for relaxed practice and freshwater wildlife watching. The lake is best known for its seasonal freshwater jellyfish and for a broad mix of fish and invertebrate life, making it feel more like a structured inland training site than an open-water adventure dive.