| GAC | Global Area Coverage | - | Scuba Diving |
| GARS | GOES Archive And Retrieval System | - | Scuba Diving |
| GASP | GOES Aerosol Smoke Product | - | Scuba Diving |
| GEOSAT | GEOdetic SATellite | - | Scuba Diving |
| GEWEX | Global Energy And Water Cycle EXperiment (WCRP) | - | Scuba Diving |
| GIFTS | Geosynchronous Imaging Fourier Transform Spectrometer | - | Scuba Diving |
| GLOBE | Global Learning And Observations To Benefit The Environment | - | Scuba Diving |
| GMS | Geostationary Meteorological Satellite | - | Scuba Diving |
| GMT | Greenwich Mean Time (repl. By UTC) | - | Scuba Diving |
| GOES | Geostationary Operational Environmental Satellite | - | Scuba Diving |
| GPS | Global Positioning System | - | Scuba Diving |
