- Category: Water Feature
- Type: Island
- Latitude/Longitude: 50°2'52"N 5°36'19"W
- Eastings/Northings: 141988, 22633
- OS Grid: SW419226
- Mapcode Local: GBR DXJK.C7D
- Mapcode Global: VH05V.S2J5
Location and coordinates are for the approximate centre of Merthen Rock within this administrative area.
Geographic features and populated places may cross administrative borders.