As most of the sea bottom in the Dutch part of the North Sea consists of sand, marine fauna that live in association with hard substrates are rarely monitored. We report here on the results of a species inventory in June 2011 done by scuba-diving while focusing on a wreck on the Dogger Bank and on rocky bottoms on the Cleaver Bank. This resulted in various new records of species for the Dutch part of the North Sea. This result appeared for a large part linked to the added value of monitoring with scuba-divers. It is therefore concluded that scuba-divers should be used in addition to the more traditional monitoring methods in which dredges and grabs are used, if one aims at getting an accurate view of the biodiversity present in marine regions like the North Sea.