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They fact-checked "salinity-matched C4"? My god they're terrible.

"The American explosive devices needed to be camouflaged in a way that would make them appear to the Russian system as part of the natural background—something that required adapting to the specific salinity of the water"

This was the most ridiculous part. I can't think of a reason they would prefer to use an explosive charge in a position visible to inspection.

Acoustic impedance of seawater varies with salinity.

Sure but that doesn’t generalize to other materials. Salinity matched C4 won’t be acoustically matched. Definitely a red herring point.

"Salinity matched" does not make any sense, and the article said nothing of the sort.

It said "make them appear ... as part of the natural background — something that required adapting to the specific salinity of the water". Making something invisible to sonar could depend on the acoustic impedance (which varies with salinity) of the surrounding water and might involve adapting the object accordingly.

Then they're apparently not very good, are they?

Hersh, fact checking:

https://twitter.com/grodira/status/1626150758017015809