Looks very interesting. I was a Sonar Tech in the Navy onboard destroyer, USS Spruance DD-963. Though the technology has changed since WWII the basics are similar, Search, Localize and Track. I remember logging 4hrs of stack time while tracking one of our LA Class subs during an exercise in the Caribbean Sea.
Approximately 95% of all sonar search is passive, "listening". Depending on the area of patrol it can be very challenging, the ocean is huge but also a very noisy environment.
-Windy
