https://en.wikipedia.org/wiki/Garum ?

Strange how such a wildly popular sauce vanished from the face of the Earth.

They still have fermented fish sauce in some parts of Southern Italy. Also, I understand the Thai and other Asian fish sauces are somewhat similar.

https://en.wikipedia.org/wiki/Colatura_di_Alici

And not just "fish sauces". Fermented fish paste adds richness and body. Even if the fishiness isn't obvious.

There's also Surströmming which is a swedish type of fermented Baltic Sea herring.

How is garum different from Asian fish sauces like nước mắm?

Also, I'd posit that Worcestershire sauce is the spiritual descendant of garum.

From my research, garum was a ticker paste that involved a lot more solids. Most fish sauces, especially the Asian ones that get used in the western world, tend to be clear.

Last time I was in Thailand I delved into foods made with tai pla. It's a sauce that is thicker and made from fish entrails. Based on descriptions of garum I've read, this seems to be very close.

It's tough to accurately describe taste and flavor in literature.

My understanding is that Worcestershire or fish sauce (like in Thai cuisine) are a close approximation.