Geograph - photograph every grid square

These spongey, slimey hummocks are exposed at the lowest tides: they don't at first glance appear to be wood at all but they are the remains of the roots and boles of trees that were submerged during a great influx of the sea here. The destructive impact of the waves has also, over the years, washed away the end of the track that once led down to the beach at the eastern end of the beach, visible in the background here.
"The submerged forest off the coast of Pembrokeshire dates back to around 6,000BC, to the beginning of the Neolithic period when the British Isles were still connected to mainland Europe. It was part of Pembrokeshire’s coastal fringe that was flooded at the end of the last ice age. The forest extends out to sea between 1 mile and just a few metres. At low tides the remains of it are revealed. Flints and tools have been found there, so researchers know it was inhabited at this time."