Best weapon for hunting submarines is bow mounted sonar, a towed sonar and most formidable weapon a anti submarine helicopter
Yes variable depth sonar is also good
But PLAN needs plenty of experience in submarine hunting it's a fine fine art to master
I would like to see PLAN excercise more with its submarine and surface fleets in deep water far from home shores
Do a cat and mouse training mission between the surface fleet and the sub surface fleet to sharpen the skills of both party's
Submarine commander needs to know the terrain and under water features where they can hide and take cover
Surface fleet need to know what they are looking for sometimes even a large cluster of fish in the oceans have signals that can make it look like there is a submarine down there that is not a uncommon occurrence
I would imagine VDS should be more effective in deep sea than TAS, since you can lower it to different depth.