If you saw this coming towards you, you'd first be terrified that it was a shark, then you'd calm down when you found out it was just a robot fish spy, and be extremely impressed instead.
The GhostSwimmer, designed by Boston Engineering, is part of the US Navy's Project Silent NEMO, and is modeled on the movement of a bluefin tuna. It's 5 feet long, weighs 100 pounds and can glide through water at a depth of up to 300 feet. At the moment, it's being tested for use as a tool for gathering geological data and weather information and inspecting ships and ports but, clearly, later down the line it could be used for surveillance and intelligence gathering - though we suspect that could lead to a lot of innocent fish being blown up as a precaution when spotted near sensitive rival Navy ports.
It's definitely the sort of thing that Q would invent: hopefully they can feature one in the forthcoming James Pond sorry, Bond, movie Spectre.
[via Mental Floss]