U.S. Navy acronym meaning Signals Exploitation Space.
SES is located on Ticonderoga class cruisers and Spruance class destroyers near the entrance to the left (port) windbreak.
Most of what goes on inside entails signals collection and the more highly classified end of ELINT, COMINT and MASINT. Essentially what this means is that if it is radiated into open space by any form of transmitter, these people are probably listening and recording. Of course doing as much within range of the coast of the United States is rather illegal which means that the majority of the work in SES goes on while the ship is close to a nation or area about which the United States is actively involved in gathering intelligence.
This is a space that you are not going to see during a tour of the ship so do not even bother asking. Typically CTRs (Cryptographic Technician, Collections,) CTTs (Cryptographic Technician, Technical,) CTAs (Cryptographic Technician, Administration,) and CTIs (Cryptographic Technician, Interpreters,) work inside with assistance from the EW (Electronic Warfare Systems Operator,) shop with issues of MASINT and ELINT. Almost all of these people carry TS/SCI (Top Secret/Sensitive Compartmentalized Information,) clearances.