They seem to be shipping over troops on small boats, I think that Russia may be leaving these places lightly defended, which is of course a mistake.
Maybe they though Ukraine wouldn't be bold enough to cross the river so they moved their troops to defend against an attack from the north/east past the Dnipro.
Instead Ukraine are like "well, free real estate". If they can get a pontoon bridge or two up then getting armour across the river would be possible, and Russia will be forced to face it or lose the rest of Kherson.