| Abbreviation | Definition |
|---|---|
| IJC | International Joint Commission |
| ILC | International Law Commission |
| IM | Immunoassay |
| IM | Intermediate Modeling |
| IMA | Institute of Marine Affairs |
| IMARPE | Instituto del Mar del Per |
| IMB | Institute for Marine Biochemistry |
| IMB | International Maritime Boundary |
| IMBL | International Maritime Boundary Line |
| IMCO | Intergovernmental Maritime Consultative Organization |
| IMEL | IAEA Marine Environment Laboratory |
| IMER | Institute for Marine Environmental Research |
| IMET | Improved METeorological Instrumentation |
| IMGG | Institute of Marine Geology and Geophysics |
| IMI | International Meteorological Institute |
| IMO | International Maritime Organization |
| IMPROVE | Interagency Monitoring of Protected Visual Environments |
| IMSAP | International Marine Sciences Affairs Panel |
| IMSL | International Mathematics and Statistics Library |
| IMSTI | Institute of Marine Scientific and Technological Information |