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From the TV footage, particularly in this configuration, the operation is very much similar to a dry dock except that instead of water pumped into the dry dock, the ship lowered itself in half submerged position to allow the client ship to float in or out.
Notice that there are 4 Keel Block (the metal/timber blocks used to support bottom of client ship) and 2 metal poles used to mark and help move client ship into pre-determined position on deck and possibly to secure the Zubir in "locked down" position.
When resting on keel blocks, Zubir may or may not be able to move from deck to water under its own power. This depends on the void space created between 868's deck and Zubir's hull bottom when the air skirt is fully inflated, and the height of this void space is greater or less than the height obstruction of thee keel block.
Of course if 868 is in half submerged position, there won't be such problem.