[MHGinTN]

That’s how it all started, if memory serves. The chemical industry came up with synthetic fibers so they lobbied Congress to outlaw hemp production. The switch was completed before the second world war finished and only a few hemp leggings and tents and naval ropes survive to this day.

[OldTCS]

I transferred off my last destroyer in late 1989, and at that time all of the mooring lines were still manila. I don't know what is in use now. I've heard there is a new synthetic called Spectra, but don't know much about it.
When I was on ship, I always distrusted the synthetic lines that were in use for other than mooring purposes, because of the potential snap-back if they parted.