Consider a billionaire living on earth today. What would be the most effective way to deploy sensors to a vast area of the earth's sea depths? (Sea depths referring to the sea floor, and slightly above.)
As far as I can tell, the best modern technologies we have for autonomous underwater vehicles are underwater gliders and tethered remotely operated vehicles. Truly wireless vehicles also seem possible from what I've read, but storing enough power for such a vehicle seems to be the bottleneck.
Since this billionaire wants to deploy instruments to the deep sea, it seems impractical to use tethers to an above water platform, since you would need miles of cabling to the surface. I'm also not sure if the theory of underwater gliders holds up under the immense pressure at such depths. However, a true "rover" vehicle seems impossible, as you can't reliably transmit wirelessly underwater, also there doesn't seem to be a good way to power such a vehicle.
Obviously this billionaire is willing to put a lot of their money into this project, but they are not willing to risk their life/freedom, so they want to avoid any sort of environmental disaster.