There is this little video of a typical walk during this trip: wind, rain, cold, like a November in May. I will give a full explanation later. Enjoy your speculations.
And you certainly will agree that this is more interesting and fresh than the score from Mario Silva...
Update: I will not lift the mystery completely but will explain the video (I have another post coming).
During WWII the Germans built a defensive wall all along the Atlantic Coast. It was breached in Normandy with great difficulty but breached nevertheless. However, it would have been equally difficult anywhere else.
On the Atlantic coast that goes from the Gironde to Spain there is a long stretch of tall sand dunes and the Germans had to build huge defenses, blockhaus, on top of dunes. By definition there is no hard ground below a dune by the sea shore. However dunes move, beaches are eroded in places and grow in other places. What you see in the clip are two set of such defenses that fell down over the decades towards the eroding shores. But not only that, they got closer to each one!!! Eventually they will become reef, disappear under water and maybe in a couple of decades will be covered by the sand of a new beach. Let's say the dunes behaved over time as a sort of quicksand.