Kit Fisto using his underwater lightsaber on Dac. A specialized pulse, known as a bifurcating cyclical-ignition pulse (alternatively termed Waterproof Casing), allowed a lightsaber to be activated underwater through the utilization of two crystals. A lightsaber that lacked these specific alterations would experience a short circuit when immersed in water, requiring subsequent minor repairs to restore its functionality.
Kit Fisto's lightsaber was equipped with a bifurcating cyclical-ignition pulse. He was seen utilizing his underwater lightsaber during both the first and second engagements on Mon Calamari. Subsequently, he documented an explanation of the pulse's operation within the Great Holocron, along with instructions detailing how to modify lightsabers to incorporate this capability. His modification gained widespread adoption among Jedi Knights throughout the Clone Wars, particularly in battles fought on aquatic planets such as Kamino and Dac. Both Ahsoka Tano's lightsaber and her shoto were designed to function effectively underwater.
Luke Skywalker discovered that Anakin Skywalker's second lightsaber possessed waterproof capabilities. He later integrated this feature into his own lightsaber. By the year 24 ABY, students at Luke's Jedi Praxeum routinely incorporated the pulse into their lightsaber designs, treating it as a standard component rather than an optional enhancement. The ancient lightsaber acquired and previously owned by Anja Gallandro was also waterproof, as was the lightsaber wielded by Cilghal. The Imperial Knights also possessed this capability in their lightsabers.