Uncrewed, remote-controlled boats have been around since the end of World War II. Late last century, technological innovations broadened their potential uses.

Lethal, advanced sea drones developed and deployed by Ukraine in its war with Russia have opened a new chapter in that story.

Ukraine claims it is the first country to set up a specific unit dedicated to producing them. Yemen-based Houthis have also deployed armed unmanned surface vessels as suicide drone boats that explode upon impact.

The 2-year-old Ukraine conflict has become a laboratory for new military technology, and naval drones are set to become an essential part of the combat toolbox in 21st-century warfare.

WHAT ARE SEA DRONES?

Unmanned vessels — also called drone boats or maritime drones — have had a broad range of applications for years. They have been employed for scientific research, search and rescue operations, surveillance and coastal patrols.

Ukraine has loaded them with explosives. The sleek vessels speed across the water’s surface, trailing a wake of white foam, and have a low radar signature that makes them hard to detect.

They are equipped with advanced GPS and cameras.

The Magura V5 sea drone that Ukraine says it used in the Black Sea on Tuesday appears to be Kyiv’s latest version. The craft wouldn’t look out of place in a James Bond movie.

The Magura is 5.5 meters (18 feet) long, weighs up to 1,000 kilograms (2,200 pounds), has a range of up to 800 kilometers (500 miles), 60 hours of battery life, and a 200-kilogram (440-pound) payload, according to Ukrainian authorities. It also beams live video to operators.

Another drone that is larger than the Madura, called Sea Baby, was shown to The Associated Press on Wednesday.

The latest Sea Baby model is capable of carrying 850 kilograms (1,900 pounds) of explosives, hits a top speed of 90 kph (56 mph) and can cover a distance of 1,000 kilometers (620 miles), according to Ukraine’s State Security Service.

HOW ARE SEA DRONES BEING USED IN THE RUSSIA-UKRAINE WAR?

The unmanned boats are being used to target Russian shipping and infrastructure in the Black Sea, which has Russian and Ukrainian coastlines.

Ukraine says the drones have sunk and damaged Russian ships there. That has helped Kyiv resume some grain exports.

Kyiv officials say some 20% of Russian missile attacks on Ukraine are launched from the Black Sea. The Ukrainian fleet lost 80% of its vessels after Russia’s occupation of Crimea in 2014, they say.

Ukrainian naval drones first struck a Russian ship in October 2022, the military claim, when they hit vessels moored off the coast of occupied Crimea.

Last July, Russia said two Ukrainian maritime drones hit the Kerch Bridge, a key supply route linking Russia to Crimea, forcing its temporary closure. Unconfirmed reports said a Sea Baby drone was used in that strike.

The following month, Ukrainian sea drones struck a Russian port and damaged a warship, officials said.

Being outgunned and outnumbered in the war against its bigger neighbor, Ukraine’s daring sea drone attacks have lifted morale.

WHERE IS UKRAINE GETTING THE SEA DRONES FROM?

Ukrainian know-how and ingenuity are behind the development of the new generation of sea drones.

They are locally designed and tested, but some components are sourced abroad.

United24, a government crowdfunding organization that elicits donations from companies and individuals worldwide, collects the funding.

Though the sea drones aren’t cheap — each Magura, for example, comes in at around $250,000 and the new model Sea Baby costs around $221,000 — they can damage or sink a ship worth hundreds of millions of dollars.

United24 says it is assembling the world’s first drone fleet.

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Vasilisa Stepanenko contributed to this report.

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Follow AP’s coverage of the war in Ukraine at https://apnews.com/hub/russia-ukraine