Countries are rapidly expanding the use of underwater drones as global conflicts highlight vulnerabilities in deep-sea infrastructure. These autonomous systems can travel long distances, monitor power and telecom cables, scan for mines and track submarines. Early underwater vehicles were developed during the Cold War, but new technology and recent attacks on pipelines and cables have accelerated investment. Germany has built the Greyshark drone, Australia is developing Ghost Shark with Anduril, the United Kingdom is expanding its uncrewed fleet, and the United States is increasing funding for its programmes. Russia has also tested its nuclear-powered Poseidon drone, signalling a wider global race.