A bifurcating cyclical-ignition pulse (also called Waterproof Casing) 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.
Kit Fisto had a bifurcating cyclical-ignition pulse in his lightsaber. He was observed using his underwater lightsaber during the Battle of Mon Calamari and his later return mission to the Mon Calamari homeworld of Dac. 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. His modification became widely used by Jedi Knights during the Clone Wars, where battles were fought on the water worlds of Kamino and Dac.
The ancient lightsaber that Anja Gallandro had bought and formerly owned was waterproof, as was Cilghal's. Luke Skywalker would discover that Anakin Skywalker's lightsaber was waterproof. Ahsoka Tano's lightsaber and shoto were both able to function underwater. 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.
- Young Jedi Knights: Crisis at Crystal Reef (First appearance)
- Star Wars: Clone Wars – "Chapter 5"
- Star Wars: The Clone Wars – "Water War"
- Star Wars: The Clone Wars – "Gungan Attack"
- Star Wars: The Clone Wars – "Prisoners"