This article summarizes the results of 27 North Sea expeditions having the objective of retrieving mammal fossils from the sea floor. These sometimes multidisciplinary trips have harvested tons of fossils and a wealth of information on the Late Pleistocene mammoth steppe and its flora and fauna, as well as an Early Holocene fauna. The study location was the Eurogeul area off the coast of Zuid-Holland. The Eurogeul, the route which large ships must navigate in order to enter the harbor of Rotterdam, is a unique Late Pleistocene submerged site which is part of the richest fossil mammoth steppe sites of Northwest Europe. The expeditions showed beyond reasonable doubt that the Eurogeul site is part of this mammoth steppe ecosystem, existing between 100,000 and 10,000 years BP, in which woolly mammoths, lions and other large terrestrial mammals thrived, while marine mammals such as walrus and beluga were frequenting the estuaries of the large rivers Rhine and Meuse and the nearby North Sea coasts.