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Most semisubmersible drilling rigs are fitted with conventional chain or combination chain and wire catenary mooring systems. These mooring systems can employ high-holding power anchors with 3" or 3 1/4" anchor chain and mooring wire of at least 3" in diameter.
 These types of systems are typically "self-contained" onboard the drilling rig. The limiting factor for conventional catenary mooring systems is their length, weight, and ability to hold the rig within the desired minimum watch circle in greater water depths.
During normal operations, the installation or recovery of these moorings is accomplished with either one or two anchor handling vessels (AHVs). Each AHV will work opposing mooring legs of the rig simultaneously while a tug is used for station-keeping assistance. Size and horsepower of the AHVs are key elements of the straightforward mooring operation.
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