A quarry near the Dutch town of Winterswijk has many fossils of marine reptiles – many of them with a surprising amount of bone material preserved intact- see https://phys.org/print466766176.html … some of the skeletons are completely preserved. Why might that be as the fossil bones go back to 240 million years agao. At that time this part of the Netherlands was submerged, it is thought. In adddition, it must have been shallow water as there are the preserved footprints of land animals. Was it certainly a submerged landscape or might the bones have been washed up and buried in a high tide – or perhaps, a tsunami wave. The fossil footprints of terrestrial animals is an especial mystery if we are talking about a seascape. The fossils, in addition, were buried in what is called sediment (mud and silt I suppose). This must have occurred quickly in order to preserve intact skeletons.