The North Sea is a marginal sea of the Atlantic Ocean. It is located in the northwestern part of Europe. It is bounded by land on three sides. The water temperature reaches up to 25 °C in summer and up to 10 °C in winter. The northern North Sea around Norway is characterized by fjords, skerries and cliffs. The southern part is known for its flat coast and for the Wadden Sea. The Wadden Sea World Heritage Site covers more than 4,000 km2. It is home to countless animal and plant species and is a unique habitat. The special climatic conditions on the German, Dutch and Danish North Sea coast are considered to be particularly beneficial to health. The interaction of the various climatic factors such as air, temperature, water, solar radiation and wind activate the circulation and immune system and have a healing effect on the skin and respiratory tract.