Britain is donating six Remus 100 UUVs (Unmanned Underwater Vehicle) to Ukraine and is currently training Ukrainian sailors how to operate them. The U.S. also has Remus 100 and successfully used them in the Persian Gulf fifteen years ago.
Remus 100 is a 37 kg (80 pound) vehicle that looks like a small torpedo. It is 1.6 meters (5.4 feet) long and 190mm in diameter. Carrying a side scanning sonar and other sensors, a Remus 100 can stay underwater for 22 hours, traveling at a cruising speed of five kilometers an hour (top speed is nearly twice that.) The UUV can operate up to 100 kilometers from its operator, and dive to 100 meters (300 feet). The UUV keeps costs down by using GPS, in addition to inertial guidance. The UUV surfaces every hour or two to get a GPS fix, and then goes back to doing what it was programmed to do. Ukraine will use them to find and eliminate Russian bottom mines in shallow coastal waters.
Remus 100 was designed mainly for civilian applications (inspecting underwater facilities, pollution monitoring, underwater survey or search). But there are similar military and police applications, like searching for naval mines. Australia and New Zealand also use Remus 100, and several hundred are in use. Depending on sensors carried, each Remus costs $350-500,000.
Britain donated two Sundown class minehunter ships to Ukraine. These are 600-ton ships with a crew of 34 and equipped with Seafox UUVs for detecting and destroying (by placing explosive charges) mines.