Why does a research institute build a new deep water model basin in 2000? Would it not be better to invest only in the development of new numerical tools, as the tools of the future? MARIN sees the worth of numerical tool development and full scale measurements. It is one of the reasons why its name in the past was changed from Netherlands Ship Model Basin (NSMB) to Maritime Research Institute Netherlands. Maritime research is more than model testing. But we are convinced that model testing is still of vital importance for the design of safe and economical offshore structures. The trend to explore deep and ultra deep water fields with moored vessels, brings us now to questions as: What is the relation between model tests and numerical simulations and full scale measurements? What are the requirements for reliable model testing? Which solutions are there for ultra deep water (> 1000 m), when even the deepest model basin does not seem deep enough? In this presentation these aspects will be discussed. And, as a case study, also some aspects of the MARIN new facilities will be discussed.