Amazon filed for a patent entitled “Aquatic storage facilities” in September 2016 that was recently granted. The aim of this patented system is to increase warehouse space by increasing storage space by depth.
The proposed system would create underground warehouses by wrapping containers of stock items in waterproof packaging with depth control devices (to raise and lower the items) and storing them in giant water pools submerged under current Amazon warehouse floors.
The patent also mentions the possibility of using airplanes or drones to drop packages (fitted with GPS tags) into natural rivers or lakes where they would be stored at the bottom of the water until they were needed and they could then be retrieved using a sonar signal.
You can read more about the patent here: http://bit.ly/2sMfdeA