It costs, bigtime, if you want to leave your shipping container on a dockside.
Today’s invention is a way to stack such boxes, whilst making the best possible use of the quayside area available.

There have been recent mathematical advances in understanding the ways in which blocks can be formed into overhanging piles. I suggest that these therefore be used to allow containers to form piles which have small ‘footprints’ and yet which can reach out, stably, over the adjacent water.
Obviously, there is some work to do in determining what the optimal order might be in terms of removing the containers when required, but the wildly expensive ground space required to form a stack can be significantly reduced.
This might also work for portakabins, apartments or even car parking pallets. It might even allow container ships to carry many more overhanging containers when at sea.