Just when you thought it was safe to go back into the water...

This makes me start humming the Sharky & George theme tune...

Sea bass, for example, have been observed diving to the bottom of the sea when they hear a loud noise. Might they do the same, in a predictable manner, when encountering an underwater vehicle? "We have a fairly good feeling that we will see that response, we just need to quantify it," says Dr Helen Bailey, research associate professor at the University of Maryland Center for Environmental Science. 

"We can implant miniature depth sensor tags on the fish so we can detect the movement, and there is already the technology in place for that to be a real-time system." She says there's no reason why an army of black sea bass couldn't provide a cost-effective warning system against enemy subs.

This feels like what would happen in Aquaman and Saruman got together with Mark Zuckerberg.

Snapping shrimp, found all over the world in shallow water at latitudes less than about 40 degrees, continuously snap their claws together, creating a constant sound signal that bounces back off surrounding objects. As with conventional sonar systems, measuring the time it takes for the sound signal to return, and its strength, can reveal the size, shape and distance of underwater objects. 

"The concept doesn't rely on the shrimp changing its behaviour in any way when the vehicle approaches, it just uses the sound it creates," says Ms Laferriere. This is important because you don't want your surveillance system to be detectable or to make its own noise that interferes with the sensors. "It's a passive system," she adds. "It will be low-power and capable of detecting even the quietest vehicles."

So basically a giant information-gathering system about hitherto uninteresting details about fish. They should call it Fishbook, or possibly MyPlaice. Maybe Grouper Plus, if it doesn't catch on. Or Fins Reunited. Twilapia, if desperate. I'll stop now. Anyway, I'd be more interested to know what this could help us learn about fish than using the poor unwitting things as spies.

How fish and shrimps could be recruited as underwater spies

We have a long history of trying to use animals as spies, weapons and warning systems, but the latest plans to use marine organisms as motion sensors may be the strangest yet. When a beluga whale was spotted wearing a harness recently, some speculated that it had been trained to spy for the Russian army.