The ships are being carried on top of
self-propelled modular transporters. They run on hydraulic power, are remote controlled and have enormous load carrying capacity, say over 1500~3000 plus tons per unit. You can join many units together like a train, forming a self propelled movable platform. The wheels can turn every which way and can take the ship over to a semi-submersible barge (see below). Which is then floated away, and slowly sunk, by ingesting water, to float the ship itself at deeper draft areas. Most elegant but slow ship launch procedure.
You guys may remember, we had these semi-submersibles come to Chittagong to deliver our Ming subs.