This curving arm is probably the southern half of a 'C' shaped fish trap. It is visible on modern (2005 and 2009) aerial photographic and LIDAR (2012) coverage. It measures approximately 130m from end to end and probably comprises a line of boulders representing the remains of dry stone walls. The apex (containing a cod-end or sluice) of the trap would have pointed towards the sea. The arm terminates at this position, and there would probably have originally been another arm mirroring the first.

Sources include:
Environment Agency, 2012, LIDAR data
National Assembly of Wales, 2005, vertical AP
National Assembly of Wales, 2009, vertical AP

Maritime Officer, RCAHMW, March 2012