Traeth-yr-ynys (pronounced 'try-thur-unn-iss') consists of sand and rocks with some small caves and is about ¼ mile long at low tide. The hill of Pen y Badell (541 feet high) is behind the beach. North facing and backed by high cliffs, it doesn't get much sun. A steep path with some concrete steps descends to the beach from the headland, with the last few feet being a scramble down the rocks. Further along the headland another steep path descends to the shore providing low tide access to the tidal island of Ynys Lochtyn. This path is approximately 20 yards from the end of the headland on the eastern side, and can be difficult to locate if you don't know where to look.
To get here from Llangrannog, you could take the coastal path, but if parking at the car park on the B4334, take the narrow lane which forks off to the right about 100 yards after crossing the stream (see map), and follow it through Lochtyn farm and onto the coastal path. This avoids some of the steep climbs. Swimming is generally safe here. The cove to the east - shown on some maps as Traeth Gaerglwyd - is backed by high cliffs and not accessible from land.
The photos were taken at low tide.