This feature is visible on modern (2005 and 2009) aerial photographic coverage, and is probably a line of putcher nets. The feature is located some 140m from the high water mark. It curves in a southerly direction for approximately 30m, before running south for a further 4m or so.

Sources include:
National Assembly of Wales, 2005, vertical AP
National Assembly of Wales, 2009, vertical AP

Maritime Officer, RCAHMW, May 2012.