Bifurcating cyclical-ignition pulse

A bifurcating cyclical-ignition pulse (also called Waterproof Casing^[1]) was a pulse that enabled a lightsaber to activate underwater with the help of two crystals. Without special modifications, a lightsaber submerged underwater would short out and would require minor repairs before working again.^[1]

Kit Fisto's lightsaber had a bifurcating cyclical-ignition pulse. He was observed using his underwater lightsaber on during the first and second battles of Mon Calamari. He would later record in the Great Holocron an explanation of how the pulse worked, and instructions on how to modify lightsabers to add the feature.^[2] His modification became widely used by Jedi Knights during the Clone Wars, where battles were fought on the water worlds of Kamino and Dac.^[2] Ahsoka Tano's lightsaber and shoto were both able to function underwater.

Luke Skywalker would discover that Anakin Skywalker's second lightsaber was waterproof.^[2] He later added this feature to his own lightsaber.^[3]^[4] By 24 ABY, Luke's Jedi Praxeum students had already created lightsabers with the pulse as part of their regular design, rather than as an optional choice. The ancient lightsaber that Anja Gallandro had bought and formerly owned was waterproof, as was Cilghal's. The Imperial Knights also had this feature.