Sea Baby marine drone (Photo: SBU)

Thanks to the underwater mines planted by the Sea Baby drones near the waters of the Crimean Peninsula, the Security Service of Ukraine (SBU) hit at least four Russian ships, according to The Wall Street Journal.

The publication states that after the initial use of sea drones by Ukraine, the Russians built larger barriers at the entrance to the port of Sevastopol, making drone strikes almost impossible.

The team of the head of the SBU Vasyl Malyuk then came up with an alternative: laying sea mines, the journalists noted.

This was done using bottom mines, made of plastic and weighing about 180 kg. They are hard to detect as they sink into the silt in shallow waters.

Malyuk's specialized team spent a month and a half tracking the routes of naval ships and civilian traffic before sending Sea Baby drones to plant two mines.

On September 14, the Samum missile corvette hit one of the mines, which punched a hole in its stern. The vessel is still under repair in dry dock.

The publication noted that in the following weeks, Sea Baby drones traveled more than 4,800 kilometers and laid about 15 more mines.

During one of the missions, detected by three Raptor-class patrol boats, the drone opened fire with a grenade launcher, hitting an enemy vessel, according to SBU Brigadier General Ivan Lukashevych, known by the call sign Hunter.

On October 11, the large patrol boat Pavel Derzhavin hit a mine while entering Sevastopol Bay for maintenance. On October 13, the boat was redirected to another port for repairs but encountered another mine while leaving Sevastopol Bay.

Journalists say that a large tugboat sent for its rescue also hit a mine and had to be towed back to port.

The WSJ noted that a few days later, an explosion also damaged the modern minesweeper Vladimir Kozitsky, one of only two in Russian service.

This was the world's first example of successful remote mining, according to journalists.

"Before, naval drones were used mostly for surveillance or logistics. We (SBU – ed.) are doing many things that no one else in the world has done before," a source told the publication.

Read also: Ukraine's SBU demonstrates new Sea Baby drones – improved and more deadly: video