Let us non saturation divers know what the acronyms are
An SBM (Single buoy Mooring) is a very large, two-part, doughnut-shaped buoy anchored to the seabed and plumbed in to a manifold delivering well-head products to a supertanker moored to the buoy. An assembly known as 'slip rings', set in the buoy, allows transmission of well-head gas and/or fluid without significant loss of pressure, while the tanker can freely rotate 360 degrees around the buoy as per wind and tide. Eight four-and-a-half-inch anchor chains secure the buoy to piled-in points on the seabed. A pipeline-end manifold (PLEM) is attached by one or two subsea hoses to flanges under the buoy—between chains one and eight. Thereafter, the product passes, via the slip rings to a rotating 'production' arm, through floating hoses to the tanker, attached by a twenty-one inch "Sampson" rope to a 'mooring' arm. The dynamic production and mooring arms sit together on top of the static section of the buoy, on three roller-bearing carriages.
Diving support is used to operate, maintain and intervene in emergencies relating to the entire top-to-bottom assembly. In India, while much of the work is not strictly diving, divers are used for all buoy operations. Clients see them as water-proof, indestructible multitaskers.
SPMS are a variant made by a different company—Single point Mooring, as opposed to SBM LTD of Monaco.
This stuff is manly, massively engineered equipment and I shall have to lie down now, exhausted by the thought of it all. I shall not take the bait for further enquiries, and respectfully suggest Wikipedia for genuine interest. I think I am having a turn...