| Abbreviation | Definition |
|---|---|
| RIBL | Rigid Inflatable Boat, Light |
| RIBM | Rigid Inflatable Boat, Medium |
| RIBS | Rigid-hulled Inflatable Boat, Small |
| RPH | Raised Pilot House |
| RPL | Ramped Powered Lighter |
| S | Schnellboot |
| S/M | SubMarine |
| SB | Small Boat |
| SBSR | Self Bailer Self Righter |
| SBSR | Self Bailer/Self Righter |
| SC | Submarine Chaser |
| SCS | Sea Control Ship |
| SD | Submarine Dutch |
| SEABEE | Sea Barge |
| SERVS | Ship Escort Response Vessel System |
| SES | Surface Effect Ship |
| SFS | Surface-Effect Fast Sealift Ship |
| SGB | Steam GunBoat |
| SIRE | Ship Inspection Report Exchange |
| SL | Self-Loading |