The US Navy is planning to arm nuclear submarines with high-energy laser weapons, according to Popular Mechanics.
But there's just one problem, according to the magazine: Laser weapons basically don't work underwater, where laser light scatters and gets absorbed almost immediately.
While public documents reveal certain details about the designs the Navy has been testing since at least 2011, the Navy has remained tight-lipped about the execution or purpose of such a system, PopMech reports. One theory, according to the magazine, is that the Navy plans to integrate the lasers into the submarines' periscopes and use them as surface weapons.
"High-energy lasers can disable the guidance systems on drones and ignite the fuel and munitions on small boats like the Iranian Boghammars," Sidharth Kaushal, research fellow at international defence think tank Royal United Services Institute, told PopMech.
It wouldn't be the US military's first foray into laser weapons. Among other efforts, the Navy has already installed a laser cannon on one of its destroyers, the US Army has signed contracts to design a military truck-mounted laser weapon, and the Air Force is testing laser weapons for fighter jets.
Based on upgrade documents, the upcoming laser system won't be mounted on Navy submarines for at least another three years, according to PopMech.
READ MORE: The Navy Is Arming Nuclear Subs With Lasers. No One Knows Why. [Popular Mechanics]
More on laser weapons: The U.S. Military Is Buying a $130 Million Laser Weapon