A California company is working on an underwater refueling station that can top off the fuel cells of undersea surveillance drones, allowing the vehicles to venture farther and work longer.

Needless to say, the US Navy is interested in that kind of technology. The sailing branch is even exploring ways to tap sea-bottom thermal vents in order to keep power flowing to underwater gas stations.

Teledyne, based in Thousand Oaks, California, showed off its undersea power station alongside Gavia, the company's popular underwater surveillance drone, at the Sea-Air-Space Exposition in Maryland in April.

The underwater fuel-cell station stores 200 kilowatts of power and works down to a depth of nearly two miles, according to Defense News. An undersea drone could hook up to the station and charge its own fuel cells. A Gavia can operate for up to five hours on one 1.2-kilowatt charge.

Teledyne is a world leader in undersea electrical equipment that's popular with the oil industry, including water- and pressure-resistant power plugs. The company also builds a wide range of torpedo-like submersible drones that are compatible with different sensors, including sonars and laser scanners.

Teledyne is proposing the seven-inch-diameter Gavia for the Navy's oceanographic fleet, which maps the sea floor. But the drone, which travels at speeds up to four miles per hour down to a maximum depth of around 10,000 feet, can also help with search-and-rescue and minehunting missions, the company points out in its marketing materials.

"The Gavia AUV can carry a variety of sensors that are especially well-suited for military and security applications," Teledyne states, using the acronym for "autonomous underwater vehicle." The Navy bought at least one Gavia for testing in 2003. Back then a Gavia cost around $150,000.

Access to undersea gas stations could allow Gavias and other underwater drones to spend more time scanning the seabed, searching for crash survivors or locating enemy mines. Teledyne told Defense News that the refueling stations could be deployed by ship or helicopter.

The Navy announced more than a decade ago that it would need to be able to refuel its growing fleet of unmanned underwater vehicles, or UUVs. "Advanced energy and propulsion, in combination with other UUV technologies, will enable the use of smaller vehicles (reducing cost) in the long term, and will provide greater performance," the Navy stated in its Unmanned Undersea Vehicle Master Plan from 2004.

In 2016, the Office of Naval Research launched the Persistent Renewable Energy for Undersea Systems program, aiming to develop systems that can "effectively recharge undersea surveillance sensor nodes and UUVs by energy harvesting from hydrothermal vents on the ocean bottom."