This large reef formed the base of huge sand-dune headlands at East Cinsta in the Eastern Cape of South Africa. I’m no geologist sadly, but the reef appeared to be a mix of sandstone and other sedimentary rocks. I cannot work out how these amazing and quite surreal rock baths were formed. At low tide these 2-5ft raised ‘baths’ were revealed. I’m guessing the sides are a harder rock than the surrounding material, but I can’t work out how the erosion took place to leave the pools. on other stretches of the reef, dark nodules of rock (from 2-7”) appeared as if loose stones scattered on the surface, but in fact were solidly attached to the reef itself.
I do wish I’d studied geology a lot further than A-level geography!