Just had a suss of the Racing
The only material allowed is SS wire.
Coated wire is a no-no.
The wire may pass through a tube with holes to let the water
3, 4 or 5mm depending on boat size.
If you're not racing
use whatever you like.
Point to note - insurance
companies are using phrases like 'as required by XXX Authority'. We have seen some policies which state the International Yacht Racing Rules as one of those XXX Authorities. Read your small print just in case.
Using Amsteel or similar has/is being done. The big downside is how do you know when it's time to replace it? With wire that's reasonably easy but with many fibres you don't know until it's to late i.e you're swimming with the fishes thinking "Damn, that had a XXX ton break load when I put it on 3 years ago." All of these fibres break down in sunlight, some quite quickly, and you can't see that happening most of the time.
Imagine the distress
if the Mother In Law fell overboard
from a dodgy rope
lifeline. Scrub that last comment and I'm of to the rope lifeline shop