I suspect that in the future, because of the proliferation of submarines, more efforts will be made on early detection and tracking.
The first of these, SOSUS, a Cold War relic, was instrumental in helping us detect new and quieter Soviet subs. And now, with the advent of very quiet diesel subs, we may need to do SOSUS one better.
In addition, there may be a need for other underwater assets, that could be unmanned and just sit on the bottom until needed. When given a signal, they release their ballast and float to the surface for whatever purpose.
Been operational over 20 years, it’s called SURTASS.