I tried some tests with Hair’s Spline Dynamics but I was getting bad behavior of the spline between the ends.
I don’t have any more time but my next guesses would be bones (let them separate for the rubber keep them connected for the steel) the problem would be the chunkiness the bones would give to the look of the ropes.
So maybe Cloth, fix the one end and belt the other to the buoy, control the stretch (or not) with the cloth properties