| Abbreviation | Definition |
|---|---|
| SL | Steam Launch |
| SOB | Single Outboard Boat |
| SoP | Spirit of Peoria |
| SOTL | Ship Of The Line |
| SP | Shore Patrol vessel |
| SR | Shallow Runner |
| SS | Fleet Submarine (Submarine type, Submarine sub-type) |
| SS | Steam Ship |
| SS(s) | small submarine(s) |
| SSB | Ballistic Missile Submarine, Conventional Powered (Submarine, Submarine, Ballistic missile) |
| SSBN | Ballistic Missile Nuclear Submarine (Submarine, Submarine, Ballistic, Nuclear) |
| SSBN | ballistic missile submarine variants |
| SSBN | submerged ship, ballistic, nuclear |
| SSG | Guided Missile Submarine, Conventional Powered |
| SSGN | Guided Missile Submarine, Nuclear Powered |
| SSK | Hunter- Killer Submarine |
| SSN | Submarine, Submarine, Nuclear (Nuclear powered attack Submarine) |
| SSN | submerged ship, nuclear |
| SSP | Submarine Submarine Personnel ( Submarine Transport) |
| SSS | Strategic Sealift Ship |