Star Wars Lightsabers Work In Water - Under One Condition
From the distinctive sound they make to their iconic design, lightsabers have been one of the most basic building blocks of the "Star Wars" universe ever since they first appeared in "Star Wars: Episode IV — A New Hope." What's more, because of what a lightsaber would really do to your body, their use results in very little blood, which is handy for a franchise loved by kids and adults alike. Still, despite their inherent coolness, there's a reason people aren't running around with lightsabers in real life. Even in-universe, there are many lightsaber rules that make no sense, so it would be incredibly difficult to make one that adheres to actual physics.
That being said, "Star Wars" does what it can to make sense of the peculiar combination of space science and mysticism surrounding lightsabers. For instance, the franchise has devoted quite some effort to explaining how the plasma blade is able to work in water. While liquid can indeed damage lightsabers, a special two-crystal upgrade called a bifurcating cyclical-ignition pulse (identified in "Star Wars" Legends) essentially waterproofs the weapon, allowing the user to wield it while submerged in any aqueous medium.
Kit Fisto pioneered the waterproof lightsaber casing
The bifurcating cyclical-ignition pulse was invented by Jedi Master Kit Fisto, who, as an amphibian Nautolan, understandably has an interest in using his lightsaber underwater. After he introduces it to the Jedi Order, it becomes a hit during the Clone Wars, remaining so popular that it becomes a common upgrade. In fact, some of the most prominent lightsabers in the "Star Wars" franchise are equipped with a bifurcating cyclical-ignition pulse, from the one Ben Kenobi (Alec Guinness) gives Luke Skywalker (Mark Hamill) in "A New Hope" to both of Ahsoka Tano's (Rosario Dawson).
Easily the most iconic personal weapons in the galaxy far, far away, lightsabers are as cool as they are versatile ... and the Jedi Knights' willingness to adopt Fisto's bifurcating cyclical-ignition pulse as a regular feature shows that they're always ready to tinker with them to make them even better.