The interdisciplinary research group DynaDeep investigates a subterranean estuary (STE) at the North Beach on Spiekeroog to a depth of approx. 25 m below surface and thus ties in with the BIME project. In the BIME project, the system was investigated to a depth of 2 m below surface. However the influence of the estuary extends deeper. Subsurface estuaries play an important role in the transport of groundwater from the land to the sea and thus also in the transport of nutrients. The goal of the research group is to study these processes in more detail and to expand the knowledge already gained about the estuary. Groundwater wells will be installed between the dune base and the low water line, and will be equipped with sensors for environmental monitoring (e.g. temperature). This will establish a measuring network that can observe the groundwater in detail over a long period of time. In addition, sediment and water samples will be taken from the ecosystem using a direct-push drilling crawler.