This may come as a surprise to the fast jet brethren and fighter jocks, but some of the original "stealth" technology put into actual military service decades before it arrived on an aircraft was on submarines. Aspect matters in that field as well when working out the ease or difficulty of a detection.
The vast majority of the sub hunting I did in my P-3 days used passive detection methods. I only used an active buoy once. Surface ships use active sonar far more.