Admiralty Sailing Directions dating to 1870 note 'Porth Nigel, more commonly known as Hell's Mouth; it has a tolerable anchorage in 10 or 12 fathoms, but it should only be used when absolutely necessary, as it has a strong indrift, and is liable to be visited suddenly by a heavy sea, rendering it both difficult and dangerous to work out.' Although no anchorage sign is shown, an historic chart notes a bottom of sand and shingle in this location with depth of 8-12 fathoms.

Sources include:
Admiralty, 1870, Sailing Directions for the West Coast of England from Milford Haven to the Mull of Galloway including the Isle of Man, pg64
Historic Admiralty Chart 1411-B5 RCAHMW digital collections sourced from the UK Hydrographic Office and first published in 1842

Maritime Officer, RCAHMW, August 2014.