The Worm's Head is joined to mainland by a rocky causeway which is exposed for 2.5 hours either side of low tide. A shallow passage for vessels for Rhossili anchorage is available vessels at highwater. Sailing Direction dating to 1884 note that it is 'one-quarter of a mile wide at highwater'. Seawater passing through the Sound creates a near shore current across Rhossil Bay.

Sources include:
Admiralty; 1884, Sailing Directions for the Bristol Channel, 4th Ed, pg91
Historic Admiralty Chart 1167_A3, RCAHMW digital collections sources from the UK Hydrographic Office published 1839
NAW Aerial Photographs 2006-9

Maritime Officer, RCAHMW, September 2014.