Porth y Nant is a very sheltered and secluded cove, about 60 yards wide, consisting mostly of rocks and shingle with a little sand. In one corner a small stream cascades down the near vertical cliffs. Access is a short and fairly easy climb / scramble down the rocks on the south side. This is one beach you'll probably have all to yourself, apart from a few oystercatchers and rock pipits.
The nearest parking is as for Fydlyn, at Grid Ref: SH303914. The photos were taken at mid-tide.