Photos

It isn't a new sport like beach-volley or beach-football in which sand increases the difficulty and hardness of a sport.
These cabins, boxes, booths can be opened and a comfortable covered sofa comes out. A way of enjoying the beach, the sun (this not so much because you lie under a roof) and refreshing air like being at home.
I can not imagine these heavy huge things in a jam-packed beach in Spain.
I have readen an article of "Spiegel on-line" of which I copied this part here:

"...German beaches are likely to be dotted with tens of thousands of covered wicker beach baskets called Strandkorb -- a feat of German ingenuity and furniture engineering.

The Germans attach a lot of importance to reliability and security, and the beach basket offers both. It protects the sitter from wind, rain and sun and is vastly superior to the common deck chair, not least because it isn't prone to sudden collapse.

typical Strandkorb seats two people. Its roof can be tilted backwards and its back reclines into a comfortable sun-bathing position. The arm rests have foldable wooden airport-style trays for mealtimes and drawers at the base make for a great place to store books, unneeded garments and snacks..."