Pictures from Zeeland, (transl. Sea land)
Deltaworks, lighthouse and coast at Haamstede and the first ones are from Yerseke (famous for its oysters and mussels) etc...
There are two types of oysters: the Zeeland oyster (Crassostrea gigas) and the Zeeland flat oyster (Ostrea edulis). The types vary considerably from each other. The Zeeland flat oyster is an expensive and exclusive product. Expensive and exclusive, because the flat oyster is rare, grows slowly and does not easily reproduce. It grows to its full size after about six years. In contrast, the Zeeland oyster can be found in large quantities in the Oosterschelde and can reach its full size within two years. With oyster spawn it is difficult to see whether it is a Zeeland oyster or a Zeeland flat oyster. This can only be seen clearly after about six months. In addition, the growth also depends on a warm (quicker) or colder season.

Oysters are bred in the Dutch Oosterschelde and the Grevelingenmeer, where the natural conditions are favourable. In the months of June and July oysters reproduce. After a few weeks the ‘spawn’ drops to the sea-floor, where it attaches on empty mussel shells. There the oyster continues its growth. Every year that the oyster grows it gets a new ring. This means that it is easy to tell how old an oyster is by its shell. After collecting the oysters, they are kept in oyster wells with fresh Oosterschelde water. The oysters purify themselves and remove their sand and silt. After a few days they are clean and can be packaged.
For info on the Delta works have a look here (it is in English!)
http://library.thinkquest.org/C001635F/engdeltawerken1.htm