UPDATE :
The US has carried out a submarine torpedo strike that sank an Iranian warship off the south coast of Sri Lanka, according to the US secretary of defence.
Pete Hegseth confirmed that the US was behind the deadly strike on an Iranian frigate that was travelling close to the Sri Lankan coast.
“An American submarine sunk an Iranian warship that thought it was safe in international waters,” Hegseth said. “Instead, it was sunk by a torpedo.”
US submarine sank Iranian warship off Sri Lanka’s coast, Hegseth says
Acoustic buoys? Your expectations may be a bit high. It took days to find the Titan submersible when they had acoustic readings, they knew where it was aiming to go, it wasn’t moving, and it wasn’t actively hiding. The ocean is rather vast.
China & Russia have subs too and when Titan went smush nobody was going to give away that they heard it, but it’s likely that if any military had cared it would have been found much sooner.