As a kid, I remember the National Geographic Mekong article of 1968. Among other things it discussed a vast, international project of dams up and down the Big Muddy. Getting all five countries to cooperate did sound a bit airy, fairy, war or no war.
I recall the Khmer word used for the ginormous catfish was “Pla-Buk.”
No mention of a native fresh-water dolphin, however.
Pla = noun - Fish
Beuk = Mekong giant catfish, Pangasianodon gigas