I think RS may be recalling conversations about cedar trees if I remember correctly.
Osage Orange hedge will last a LONG, LONG time. I found a old school wagon hitch in the creek bottoms made from hedge at my place...it had to be 70 years old. And, the fence posts at my place (established in the 40's) were still very viable so long as they were bigger than 5 inches in diameter.
They're magical! Being completely submerged has got to speed up the process some, but they will be a one time installation and stumps/logs should outlast the pond.
