Traeth Cwmistir (above) is a beach of mostly shingle and a few large rocks on the Llyn Peninsula's north coast. It is backed mostly by banks of boulder clay and access to the shore is down a short permissive path from the coastal path.
A short distance to the east is Porth Brynogolwyd (below), which is a cove of mostly shingle to which access is a scramble down a rough path and rocks. On the western side of the beach is a smaller cove with a waterfall and a small rock arch. According to local folklore a cave immediately right (facing inland) of the waterfall was a smugglers' tunnel which ran to a nearby farm, but like most such tales it's not true as the cave is only about 15 yards long.
The photos were taken at mid tide.