[walrus01]

only the very tiniest of container ships have their own cranes onboard, anything above the tiniest size is entirely dependent on shore handling cranes.

also moving cargo between two ships floating around at sea is dangerous and difficult, giant ships are not meant to hold position parallel to each other in the open ocean (or indeed closely parallel to anything) without the assist of many tugs.

a "geared" (with crane) container ship looks like this, and even so it would be a very risky move to use the crane to do anything other than load a container to/from a wharf while the ship was firmly moored to it.

https://www.google.com/search?q=geared+container+ship&client...

[a3n]

Transferring items between ships at sea is not done while "stationary," it's done by both ships underway in parallel.

It's relatively dangerous, both ships have to be designed for it, and both crews have to be trained for it.

I participated in many such refueling and replenishing operations while I was in the US Navy.

https://www.google.com/search?tbm=isch&q=resupply%20at%20sea...

https://en.m.wikipedia.org/wiki/Underway_replenishment