In the wake (you should pardon the expression) of China's seizure of a US hydrographic research drone submarine, and its subsequent return, I've been reading up on the use of unmanned underwater vehicles (UUV's) around the world. It turns out they're a flourishing industry. Rear-Admiral Tim Gallaudet of the US Navy said recently:
In the wake of multiple news reports about U.S. Navy ocean gliders, there have been numerous questions about these instruments and what they do for the U.S. Navy.
Ocean gliders are autonomous underwater vehicles used to collect oceanographic data in an effort to better understand the ocean. The gliders are made by Teledyne Webb and are sold commercially. The Navy uses the gliders to collect ocean temperature, salinity and depth information, and transmit the unclassified data to Naval Oceanographic Office (NAVOCEANO) for assimilation into NAVOCEANO’s operational ocean models. They are used by scientists and professionals around the world working in academia, the oil and gas industry as well as the military. Gliders have been the workhorses of the operational Naval Oceanography program for nearly two decades.
. . .
The gliders are piloted by personnel within NAVOCEANO’s Glider Operation Center (GOC) 24 hours a day, seven days a week at Stennis Space Center. In the event that the GOC loses contact with the instruments, they remain afloat in the ocean until located and recovered.
. . .
Why does the Navy use gliders? Only 5 percent of the world’s oceans have been explored. These underwater robots allow us to explore more of the ocean, and faster, at a fraction of the cost of a manned submersible or a ship. The information gathered allows us to better predict ocean currents, density, sea states and tides which the U.S. Navy needs to safely and effectively operate all around the world. Once deployed, a glider can persistently sample the ocean for months freeing the ship to perform other functions ... We have approximately 130 of these gliders and they are relatively inexpensive. The U.S. Navy will not only continue to use these technologies to improve our knowledge of the oceans, but we will be significantly increasing our use of gliders over the coming years so that our understanding of the ocean is the best in the world.
There's more at the link.
Of course, the data gathered by these 'gliders' (semi-autonomous UUV's) can be used for civilian or military purposes. Improved charts of the ocean floor, etc. are useful to every sailor. However, for military purposes, knowing where the thermoclines are in the world's oceans can be very valuable to help avoid detection (or detect enemy ships), and if one knows where undersea mountains are, one's submarines can avoid running into them, as USS San Francisco did some years ago.
Even more interesting is the wide variety of UUV's currently under development for, or in service with, the world's navies and research laboratories. Navaldrones.com has exhaustive lists of the various drones, and the efforts of their countries to develop more. Click over there to select a model from their drop-down lists and read about it in more detail. I think you'll be surprised at how many there are. Some are being developed as weapons of war, to detect and disable mines, and potentially enemy submarines as well as the UUV's become more advanced. The field is progressing fast. Who knows what may go into service in the next decade?
(And that also explains why China wanted to check out the latest US UUV technology . . . )