There are plenty of nude beaches in Holland. You will find many beaches for nude recreation along the coast, on the Wadden Islands and along the many inland lakes. Most of these nude beaches have been allocated by the government and are clearly marked with a sign. There are also many informal nude beaches that spontaneously emerged because they were being used for nude recreation.
Every day is different
Whether or not these informal nude recreation spaces are formally allowed depends on local and national legislation. However, it is certainly legal if there are no other recreationists using the beach. There are even beaches where the first people to arrive decide whether there will be nude or dressed recreation there on that particular day.
Formally, it is not compulsory to be nude on a nude beach—but it is expected. Young people (teenagers) who come along with their parents but feel uncomfortable naked are of course allowed to wear a bathing suit. Explicitly watching others and overly intimate behaviour is not appreciated, but overall the Dutch are far from prudish and very tolerant.