I enjoyed the seascape but I looked down much too often. The beaches of the Maasvlakte have been dredged from deep sand beds dating to the ice ages. This means that you can find fossil teeth and bones there. I'm addicted to that kind of thing. There is a whole website that catalogues and identifies the finds from this beach.
I was not looking for fossils, I was looking for ventifacts. I was triggered by the sand blowing in the wind at ankle height, stinging my bare feet. And indeed I found many wind-polished stones, with a shiny top and a matte bottom. Strange stones I had never seen before. The size, colour and sheen of fresh chestnuts. The weight, feel and sound of flint.
At first I thought they might be fossilized bones, vertebra, teeth or something similar. But after breaking two specimens with a hammer I saw that they had the colour and consistency of sandstone, not of bone, and also not of flint.
beach find website: nodules of the mineral limonite. It fits all the criteria: it breaks in a shell-like manner and produces a yellowish mark when scratched against a rough surface. It contains a high concentration of iron. Excellent pictures can be found here. Limonites are often erroneously identified as meteorites. But not by me!