The Soviets didn’t have titanium hulls on at least some submarines?
I can see those things being dumped by the thousands with little pingers on them. They would have to die sometime though since if they didn’t the ocean would have to be littered with little pingers. Clappers and simple and cheap though.
A few and long after this experiment. I joined the Air Force in 1973 and this was the stuff of legend in the ASW community long before then.
https://en.wikipedia.org/wiki/Alfa-class_submarine
Alfa (Project 705) submarines had titanium hulls.
And were outrageously expensive for the Soviets to keep up.
They were all gone by the mid-90’s.