I mean if the container cranes were destroyed at the destination port.
a loaded forty foot container is rated for up to 60,000 pounds so it would take a big mobile crane of which there some, but nowhere near the capacity of a modern container port crane.
On my island in the Caribbean, the container port uses mobile cranes, not the big gantry cranes at say,Long Beach. A container takes about thirty to forty minutes from the time the longshoremen climbing up the container stack to guide the spreader bars into place to when the it is driven off the dock.
Even if it's a half hour, that's only forty eight containers a day working twenty four hours.A big port like Long Beach or NYC currently does forty eight THOUSAND a day.
So the answer to your question is: very very slowly.
Some would move vessel to shallow water, open seacocks to
flood hull, to either topple deck cargo overboard or power winch
same containers aside onto barges. Low tide could allow track-
driven haulers to access toppled cargo for cable coupling and
drag of loot up above high tide reach. Welding cut of hull follows
to gut ship interior of metal scrap, vessel equipment, and cargo.
Donkey engines ashore could assist cable pull. YouTube video
about ship-breaker industry of the Indian Ocean extracting value
shows the business details. Port off-loading equipment is faster
and returns the ship for continued commerce but not everyone
can be bothered to do that. Wreckers have existed since the Age
of Sail, legitimate and illegitimate, as all shipping is an opportunity.
They wouldn't need to.
If "the container cranes were all destroyed" they wouldn't be able to put them on the ships in the first place!
They couldn't. I would imagine they would erect temporary or portable cranes to offload the containers, but it would take a very long time. Easier to route the ship to another port with functioning cranes and rail or truck the containers to the proper place.
Containers can be unloaded using a regular (all be it large) conventional mobile crane.
But basically you need some sort of crane…
They wouldn't, the containers weigh too much to lift by hand and the inventory is by container, not what is in them.
Go to Home Depot and hire some cheap day labor. Hey wait…you're not a terrorist planning a harbor attack are you? NSA watches this site pretty heavy and I'd hate to get in trouble for aiding a terrorist attack….