| Abbreviation | Definition |
|---|---|
| PEQUOD | Pacific Equatorial Ocean Dynamics |
| PERS | Pacific Estuarine Research Society |
| PERT | Performance Evaluation and Review Technique |
| PETA | People for the Ethical Treatment of Animals |
| PFC | Perfluorocarbon |
| PFZ | Polar Front Zone |
| PHM | PHreatoMagmatic |
| PHN | Plan Hidrológico Nacional |
| PI | Principal Investigator |
| PICES | North Pacific Marine Science Organization |
| PILN | Pacific Invasives Learning Network |
| PIMRIS | Pacific Islands Marine Resources Information System |
| PIMS | Pacific Institutes of Marine Science |
| PIN | Pacific Island network |
| PIPICO | Panel for International Programs and International Cooperation in Ocean Affairs |
| PIRATA | Pilot Research Moored Array in the Tropical Atlantic |
| PIREPS | Pilot Reports |
| PL | Public Law |
| PLGR | Pre-Lay-Grapnel-Run |
| PLRF | Program on Long-Range Forecasting Research |