- Category: Water Feature
- Type: Island
- Latitude/Longitude: 49°54'37"N 6°17'36"W
- Eastings/Northings: 91857, 9977
- OS Grid: SV918099
- Mapcode Local: GBR BXVX.G24
- Mapcode Global: VGYC4.VJP1
Location and coordinates are for the approximate centre of Mainmark Rock within this administrative area.
Geographic features and populated places may cross administrative borders.