British sailors are drilling to fend off potential drone attacks against £4 billion ($5.3 billion) Vanguard-class subs using fire hoses as the only onboard “air defense weapon,” The Sun has reported.

The hoses, known as “center fed reels” are placed on submarine decks as a precaution when the vessels are moored at the British naval base Clyde in Scotland, the UK’s most sensitive military site, the tabloid reported on Thursday, citing anonymous sources. The equipment has pistol-grip nozzles that would allow sailors to direct water at approaching drones.

“You have to use what you’ve got,” the tabloid cited one of its sources as saying.

The Royal Navy’s four Vanguard-class ballistic missile submarines are the only British platforms equipped to carry and launch Trident II nuclear missiles, which deliver the UK’s only operational nuclear weapons. According to The Sun, the Navy insists that layered defenses, including “physical barriers, patrols, surveillance, monitoring, and counter-drone capabilities,” protect the subs.

The report comes as the Royal Navy is facing what a former senior commander has described as its worst crisis in 350 years.

The UK’s entire fleet of nuclear-powered Astute-class attack submarines are not fit for combat duty, retired chief of the Naval Staff, Lord Alan West, told The Sun earlier this year. Five of the vessels are facing maintenance and availability delays, while the sixth, according to the Royal Navy, is still undergoing sea trials ahead of returning to service.

West described the number of ships the Navy has as “pathetic.” The fleet has just five operational frigates and no amphibious assault ships, while former Prime Minister Keir Starmer’s government retired four frigates, two assault ships, two tankers, and a nuclear-powered submarine during his time in office, The Sun reported in July.

This year, the UK has pledged an additional £15 billion in military funding, citing alleged threats from Russia. London has also seized and aided in seizing ships it has accused of being part of the so-called Russian ‘shadow fleet’ – a practice Moscow has denounced as “piracy.”

Russian President Vladimir Putin has dismissed claims that Moscow wants to attack NATO and has accused Western European leaders of escalating tensions with Moscow, pointing to their statements about preparing for a possible war with Russia in 2029 or 2030, repeated military exercises in the Baltic Sea, and attempts to detain Russian vessels. “This is all escalation,” he said last week.