Imagine sitting in a plastic bathtub, but instead of being rounded, it's made of triangular facets. The edges where they join are not quite hinges, but they flex so that the whole compartment changes shape.
Hard caked sand, more like sandstone really, encapsulates the plastic seat so that it's like a body, and four long stilt-like sandstone legs reach down to the beach. Altogether, it's a strange sandstone headless animal-shape.
As we rock from side to side in the seat, our shifting weight makes the triangles flex, and the rocky legs walk across the sands in a strange camel-like gait.
Bits of sand break off and fall to the beach with every step, as the flexure pops off little chunks or puffs of dry sand.
Back at the tent, the people running the business are busy packing sand back onto the steeds that have been returned, significantly lighter than when they left.