Many of the coasts along Limfjorden are sandbank coasts, where longitudinal, shallow sandbanks break up deeper, dark areas.
The bottom is predominantly sandy but larger rocks, areas with gravel, and underwater vegetation, break up the uniformity. The deeper areas between the sandbanks usually hold a lot of seatrouts. These areas are often called an indentation. At high tide, the seatrouts are often found in the inner, dark belt, which you can fish from the beach. However, at low tide, it might be necessary to wade out to 1. Or 2. Sandbank.
But be careful, it can be dangerous to wade out too far!