The options for riser lines that may be considered are steel chain, steel cable and synthetic rope.
ChainChain is the most common material used for mooring lines. The image below (Viking, 2010) shows studless link chain, which is the type used for permanent moorings. Chain is available in a range of diameters and grades.
[Source: Viking Moorings(2010)]
Steel CableAn advantage over using chain, particularly in this design, is that for the same breaking load it has a lower weight and higher elasticity. The higher elasticity is a necessary feature of taut leg moorings. It can be more prone to damage and corrosion than chain. The image below (Viking, 2010) shows steel cable with spiral strands and galvanized protection.
Steel Cable - Spiral Strands with galvanized protection [Source: Viking Moorings(2010)]
Synthetic RopeThese are essentially ropes made up of a series of strands of man-made fibre. They are lightweight, have high elasticity and are practically neutrally buoyant. A disadvantage is that being subjected to cyclical loadings they will need to be regularly inspected and replaced, perhaps annually. The image below (Viking, 2010) shows a synthetic rope with sand barrier and protective coating.
Synthetic Rope - Cores with sand barrier and protective coating [Source: Viking Moorings(2010)]