Title: SSN (hull classification symbol)
Content:  An SSN is a nuclear-powered general-purpose attack submarine. SSN is the US Navy hull classification symbol for such vessels; the SS denotes a submarine and the N denotes nuclear power. The designation SSN is used for interoperability throughout NATO under STANAG 1166, though navies use other terms.
Title: SSK (hull classification symbol)
Content:  SSK was the United States Navy hull classification symbol for a diesel-electric submarine specialized for anti-submarine duties. SS indicated that the vessel was a submarine, and the K suffix that it was a hunter-killer. The United States Navy does not currently operate any submarines of this type, and so the designation is inactive.
Title: Submarine Warfare insignia
Content:  submariner will be treated as a full member of the crew. Although not condoned by senior supervisory personnel, the tradition of 'tacking on' dolphins whereby other qualified sailors punch the dolphin badge while worn on the newly qualified sailors breast is a time-honored tradition in much the same way as 'tacking on' the Crow of newly promoted 3rd Class Petty Officers has been tolerated. Appropriate annotations are made in the new submariner's service jacket to reflect his qualification. Submarine qualified personnel are designated "SS" after the rate, such as STS1(SS) or MM2(SS). The "SS" stands for submarine specialist (OPNAVINST 1414.9).
Title: List of U.S. Navy acronyms
Content:  Naval Warfare Systems Command ; SPAWARSYSCEN – Space and Naval Warfare Systems Center ; SR – Seaman Recruit ; SRB – Selective Reenlistment Bonus ; SRW – Shutdown Roving Watch ; SS – Submarine Specialist ; SS – Submarine, class/type of ship ; SSBN (aka Boomers) – Hull classification symbol for ballistic missile submarine (Submersible Ship Ballistic Nuclear) ; SSES – Ships Signals Exploitation Space: compartment on a ship where embarked NAVSECGRU personnel, known a Cryptologic Technicians, do their work ; SSGN – Hull classification symbol for cruise missile submarine (Submersible Ship Guided Missile Nuclear) ; SSMG – Ships Service Motor Generator; used to produce AC electricity using main battery power on submarines ; SSN – Hull 
Title: List of acronyms: S
Content: ss – (s) Swati language (ISO 639-1 code) ; SS ; (s) Sand Storm (METAR Code) ; (p) Schutzstaffel (German, roughly "Protection Squadron"; Nazi elite Praetorian guard) ; (i) U.S. Secret Service ; Spanish Ship ; Stainless steel ; Stockholm Skins ; (s) Submarine (US Navy hull classification) ; (i) Super Sport ; Surface-to-Surface (missile) ; SSA ; (s) Cargo Submarine (US Navy hull classification) ; (i) Social Security Administration (U.S.) ; Statistics South Africa ; SSB – (a) Single-sideband modulation ; SSB – (i) Sacramento Sustainable Business ; SSBN – (s) Nuclear-Powered Ballistic Missile Submarine (US Navy hull classification) ; SSC ; (i) Safe, Sane, Consensual (SM phrase) ; Secondary 
Title: Hull classification symbol
Content:  Training Submarine ; IXSS: Unclassified Miscellaneous Submarine ; MTS: Moored Training Ship (Naval Nuclear Power School Training Platform; reconditioned SSBNs and SSNs) Submarines are all self-propelled submersible types (usually started with SS) regardless of whether employed as combatant, auxiliary, or research and development vehicles which have at least a residual combat capability. While some classes, including all diesel-electric submarines, are retired from USN service, non-U.S. navies continue to employ SS, SSA, SSAN, SSB, SSC, SSG, SSM, and SST types. With the advent of new Air Independent Propulsion/Power (AIP) systems, both SSI and SSP are used to distinguish the types within the USN, but SSP has been declared the preferred term. SSK, retired by the USN, continues to be used colloquially and interchangeably with SS for diesel-electric attack/patrol submarines within the USN, and, more formally, by the Royal Navy and British firms such as Jane's Information Group.
Title: List of U.S. Navy acronyms
Content:  symbol for general-purpose fast attack submarines (Submersible Ship Nuclear) ; SSOQ – Senior Sailor of the Quarter ; SSOY – Senior Sailor of the Year ; SSTG – Ships Service Turbo Generator ; STG – Sonar Technician Surface ; STREAM – Standard Tension Replenishment Alongside Method ; STS – Sonar Technician Submarines ; SUBRON – Submarine Squadron ; SUBSAFE – Submarine Safety Program ; SUPPO – Supply Officer ; SWCC (swick) – Special Warfare Combatant-craft Crewmen, the Special Operations Forces who operate and maintain an inventory of boats used to conduct special operations missions or to support special operations missions conducted in maritime environments, particularly those of the U.S. Navy SEALs. ; SWO – Surface Warfare Officer 
Title: Naval tradition
Content:  A naval tradition is a tradition that is, or has been, observed in one or more navies. A basic tradition is that all ships commissioned in a navy are referred to as ships rather than vessels, with the exception of submarines, which are known as boats. The prefix on a ship's name indicates that it is a commissioned ship. For example, USS is an acronym which expands to United States Ship; in the Royal Navy, HMS expands to Her Majesty's Ship (or when a King reigns, His Majesty's Ship); in the Indian Navy, INS expands to Indian Navy Ship, and so forth. An important tradition 
Title: List of acronyms: S
Content:  scale ; SSK – (s) Hunter-Killer Submarine (retired US Navy hull classification) ; SSKP – (i) Single-Shot Kill Probability ; SSL – (i) Secure Sockets Layer ; SSM – (i) Surface-to-Surface (Guided) Missile ; SSN ; (s) Nuclear-Powered Attack Submarine (US Navy hull classification) ; (i) SIM Serial Number ; Social Security Number (U.S.) ; Socialist Solidarity Network ; Subsystem number (SCCP, SS7) ; SSNW – (i) Same Shit, New Wrapping ; SSO – (s) Submarine Oiler (retired US Navy hull classification) ; SSP – (s) Submarine Transport (retired US Navy hull classification) ; SSR ; (s) Radar Picket Submarine (retired US Navy hull classification) ; (i) Solid State Recorder 
Title: Ballistic missile submarine
Content:  SSBN is the US Navy hull classification symbol for a nuclear-powered, ballistic missile-carrying submarine. The SS denotes "submarine" or "submersible", the B denotes "ballistic missile," and the N denotes "nuclear powered." The designation SSBN is also used throughout NATO under STANAG 1166. In the US Navy, SSBNs are sometimes called Fleet Ballistic Missile submarines, or FBMs. In US naval slang, ballistic missile submarines are called boomers. In the UK, they are known as bombers. In both cases, SSBN submarines operate on a two-crew concept, with two complete crews – including two captains – called Gold and Blue in the United States, Starboard and Port in the United Kingdom.

Question: what does ss stand for on naval ships?
Answer: Single-screw Steamship.