https://youtu.be/eR8TQ2rXTbE?t=119
Dang read up on USS San Francisco briefly and ran across this tidbit about sonar, dang.
> For those who dont know how tremendously loud it is. It can be used to kill enemy divers if they are near your ship. It will rupture your lungs at 200 Db and hemorrhage your brain at 210 Db, sonar operates at 235 Db ... also affects sea life
Outside of major shipping lanes there's almost zero economic reason to map the areas immediately outside of your own economic zones
The problem is that navigation-quality sonar gives away the position of the submarine, which is the polar opposite of what the Navy has submarines to do.