Sentence:  For example , the importance of the Regulus 2 , , a very promising aerodynamic ship to surface missile designed to be launched by surfaced submarines , was greatly diminished by the successful acceleration of the much more advanced Polaris ballistic missile launched by <WSD>submerged</WSD> submarines . 
Meaning of the word marked with <WSD> tags:  sink below the surface; go under or as if under water