- Category: Water Feature
- Type: Island
- Latitude/Longitude: 50°27'10"N 5°2'24"W
- Eastings/Northings: 184286, 65856
- OS Grid: SW842658
- Mapcode Local: GBR ZF.JK8P
- Mapcode Global: FRA 07BV.N80
Location and coordinates are for the approximate centre of Ontonna Rock within this administrative area.
Geographic features and populated places may cross administrative borders.