It seems we've made progress:
The U.S. Navy is taking advantage of new software, and cheap, but massive, computer power, to provide an edge against non-nuclear (and very quiet) submarines operating in coastal waters. The most effective way of hunting down subs is via helicopters or maritime patrol aircraft equipped with homing torpedoes and sonobuoys. ...
The data analysis systems look for faint patterns left by submarines slowly moving through coastal waters. This takes into account the underground geography, and the activity of undersea animals and plants. The number and pattern of deployed sensors would also be taken into account.
New pattern analysis software was developed, and quiet diesel-electric subs from allies were used to test and refine the system. ...
The U.S. has been scrambling to develop the ability to detect the new generation of quiet diesel-electric subs. You won't hear any official pronouncements about progress in this area, for obvious reasons. There is progress, and just how much won't be publicly known until these new anti-submarine methods are used in combat.
It looks like we are closing a dangerous gap in our defense capabilities.
