See the hundreds of sea drones the US Navy is experimenting with overseas

Sea drones are deployed in combat to gather intelligence, conduct surveillance and reconnaissance, sweep mines, and protect critical underwater infrastructure.

Coming in a variety of designs, sizes, and capabilities, military sea drones can range from armed speedboats to minehunting miniature submarines. They can be equipped with high-definition cameras and advanced sonar to help them navigate murky depths.

Sea drones also protect crewed vessels in the fleet like aircraft carriers and submarines, acting as a first line of defense in hostile territories.

Through the Pentagon's Replicator initiative announced in August 2023, the US Department of Defense plans to field thousands of low-cost drones over the next two years to counter threats on land, in the air, and at sea.

Replicator is a fast-track effort to field and deploy thousands of combat drones within two years and at a scale that could threaten an adversary like China.

"Ukraine has shown how effective they can be and how they can be employed in current operations," Bryan Clark, a former US Navy officer and advisor on autonomous craft, told Reuters.

Clark, a senior fellow at the Washington, DC-based think tank Hudson Institute, added that the Navy "needs to embrace that lesson" and field combat sea drones "right away."

He estimated that the US is operating about 200 sea drones in counting — 100 small drones on the surface and another 100 underwater.

For more than three years, the Navy has been studying the integration of autonomous vessels in its fleet through a handful of task forces, notably Task Force 59, the first naval unmanned and artificial intelligence task force.

TF 59 has "tested, upgraded, evolved, and operated with more than 23 different unmanned systems," according to the Navy, integrating them into maritime operations in the Middle East.

As the Navy continues to test sea drones' operability with its crewed fleet, the US has already been deploying drone boats to monitor adversaries. In October 2023, a dozen different unmanned and manned vessels participated in an operation that tracked Iranian warships and gunboats in and around the Strait of Hormuz, US Naval Forces Central Command said at the time.

The Navy used a fast-interceptor USV called the Arabian Fox MAST-13 to capture photographs of the Iranian boats, drones, and helicopters that were harassing commercial vessels and American military vessels transiting in Middle Eastern waters.

The US Navy is experimenting with several different drones, including the Triton, a drone built by marine engineer Ocean Aero and backed by Lockheed Martin.

As the world's first and only autonomous underwater and surface vehicle (AUSV), the Triton can operate in sailing mode or submarine mode with its interchangeable sail.

The 14.5-foot drone can sail at about 6 mph and submerge up to 328 feet deep. The Triton is powered by rechargeable batteries fueled by solar and wind power, allowing the drone to operate autonomously for as long as three months.

While the Navy is largely experimenting with sea drones in the Indo-Pacific and Middle East, the service has also been studying the integration of the Triton in the Mediterranean and the Gulf of Guinea.

Saildrone, a California-based ocean drone manufacturer that builds autonomous vehicles by the same name, has three drone variants under contract with the US Navy.

With a length of 65 feet and a weight of over 33,000 pounds, the Saildrone Surveyor, which was built specifically for the Navy, is the world's largest autonomous ocean-mapping vehicle class in operation. The diesel-powered drone employs an advanced radar and camera system, echo sounders, and sensors to map and monitor its environment, remotely transmitting the data with advanced machine learning anywhere in the world.

Late last year, the US Navy also deployed 10 Saildrone Voyagers as part of its efforts to build a hybrid fleet. Powered by solar and wind energy, the Voyager is designed to be an environmentally friendly, midsize autonomous platform, clocking in at about half the size of the Surveyor. It is equipped with a suite of sensors and instruments, like smart cameras, digital radar, and subsurface passive acoustics.

With a hull length of 23 feet, the Saildrone Explorer is the smallest USV built by the company but can still carry an array of advanced sensors and radars to collect high-quality data at sea.

Military shipbuilder Huntington Ingalls Industries developed a minehunting drone known as the Remus 300. This small, portable unmanned underwater vehicle can be launched like a torpedo from a ship or submarine.

The Remus 300 can reach depths of up to 1,000 feet and operate for up to 30 hours on missions including reconnaissance and anti-submarine warfare, as well as minesweeping.

Last October, the Navy awarded a $347 million contract to HII to develop drones for its Lionfish program, which is focused on deploying autonomous craft in the Indo-Pacific. The initial purchase late last year was for nine small underwater drones — worth about $19 million — with the potential acquisition of up to 200 over the next five years.

Naval drones are known for their effectiveness in surveillance, but Navy officials are also attempting to boost their lethal capabilities.

In an exercise last November, the Navy said it fired live weapons from unmanned surface vessels in international waters near the Arabian Peninsula — the first time lethal munitions were launched from American drone boats in the Middle East.

The Navy equipped a T38 Devil Ray USV, a speedboat-like drone developed by Florida-based manufacturer Maritime Tactical Systems, with a loitering precision-guided lethal system known as a Lethal Miniature Aerial Missile (LMAM). The 38-foot unmanned boat has a payload capacity of 4,000 pounds and travels at speeds of 80 to 115 mph, making it one of the world's fastest-known attack boats.

With a human operator ashore controlling the USV, the T38 targeted and engaged with target boats simulating hostile forces at sea and "successfully scored direct hits each time," NAVCENT said in a statement.

Sea drones can operate with varying levels of autonomy, from having a human operator at the wheel to using artificial intelligence and smart technology to carry out tasks.

Produced by Ocean Power Technologies, Wave Adaptive Modular Vessel, or WAM-V, is an autonomous surface vehicle (ASV) that uses suspension technology to collect data with a low carbon footprint.

The ultra-light, modular ASV has a spider-like chassis mounted on two pontoons that give it a shallow draft of just under two feet, allowing it to operate in areas where traditional survey vessels are too large to reach.

The WAM-V is equipped with side-scan sonar, a 180-degree camera, and a multibeam echo sounder, capable of remote observation, systems delivery, and infrastructure inspection.

Sea drones could be key in the US efforts to deter a Chinese invasion of self-ruled Taiwan, which China views as a breakaway province that should be under Beijing's control.

As the largest drone producer in the world, China is likely to employ autonomous warfare amid heightened tensions with Taiwan. But experts speculate a potential conflict in the South China Sea could differ from what is happening in the Red and Black Sea.

In 2022, China's People's Liberation Army Navy launched the world's first high-tech unmanned carrier. The Zhu Hai Yun is capable of deploying dozens of aerial and maritime drones that can scout for and target US warships and submarines aiding Taiwan.

The PLA Navy could also deploy decoys throughout the South China Sea to "make it difficult for American missiles and submarines to distinguish between high-value ships and worthless uncrewed commercial vessels," according to a report from the Center for a New American Security, a DC-based wargaming think tank.

Nonetheless, the top US admiral in the Pacific said the US Navy is prepared to deploy an unmanned fleet of its own if China invades Taiwan.

Adm. Samuel Paparo, the commander of the US Indo-Pacific Command, told The Washington Post in June that he wants to "turn the Taiwan Strait into an unmanned hellscape" to fight Chinese invading forces.

"I can make their lives utterly miserable for a month, which buys me the time for the rest of everything," Paparo said.

The Pentagon's Replicator program aims to match China's naval power as the PLA's autonomous fleet continues to grow. However, the ambitious US initiative has its own obstacles.

Plagued by a defense budget that is already stretched thin, the US Navy budgeted $172 million to acquire small- and medium-sized sea drones in 2024 and just over $100 million in 2025 — not to mention the research, development, testing, evaluation, and crew training involved in addition to procurement, Reuters reported.

The Pentagon also has to rely on American or non-Chinese drone manufacturers to build its autonomous fleet, which could take longer given China's dominance in the commercial drone market.

"It can be fast, cheap, or good," Sam Gray, a retired Navy officer who now serves as executive director of the Silicon Valley Defense Group, told Defense News. "Pick two."