Shadowing fishermen’s nets with a robot sub

On a cold, clear day in November, the Donna Kathleen rode a gelid swell off the central California coast. On the aft deck of the 58-foot vessel, a small knot of people in hard hats ministered to what looked like a glorified toboggan with a couple of thrusters bolted on.

The fridge-sized, black-and-seafoam-green machine, dubbed the Beagle, was a remotely operated vehicle, or ROV — essentially, a boxy, unmanned robot submarine. As a veteran ROV designer named Dirk Rosen fiddled with one of the video cameras mounted on it, he waxed decidedly un-lyrical about the machine’s inherent hydrodynamic flair.

“It’s a total brick,” said Rosen. “It’s basically a pickup truck carrying a whole bunch of sensors.”

As Rosen paid out a thick umbilical cord attached to the Beagle, a crane lifted the machine over the deck railing and gently set it into the water, where it bobbed on the swell. Then the ROV burst to life. Like a dog sniffing out a scent, the Beagle zipped 20 feet through the water and then burbled into the dark depths below.

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