| Abbreviation | Definition |
|---|---|
| NMC | National Marine Center |
| NMDIS | National Marine Data and Information Service |
| NMEA | National Marine Educators Association |
| NMEFC | National Marine Environmental Forecasting Center |
| NMFS | National Marine Fisheries Service |
| NMHC | Nonmethane Hydrocarbon |
| NMPIS | National Marine Pollution Information System |
| NMPIS | National Marine Pollution Information Systems |
| NMPPO | National Marine Pollution Program Office |
| NMRI | National Maritime Research Institute |
| NMSP | National Marine Sanctuary Program |
| NMU | National Maritime Union |
| NNT | Nearest Neighbor Tool |
| NOA | National Oceanography Association |
| NOAA | Nautical Organisation For Atmospheric Analysis |
| NOAAPORT | Naval Ocean and Atmosphere Research Laboratory |
| NOARL | National Ocean Communications Network |
| NOCN | National Oceanographic Data Center |
| NODC | National Oceanographic Facility |
| NOF | National Ocean Industries Association |