The plasma torpedo, or e-plasma torpedo, is a type of underwater thermonuclear ordnance of seaQuest DSV 4600.
In use as early as 2017 CE, plasma warheads can be configured with variable explosive charge, which allow tactical precision from disabling ships versus full destructive potential (DSV: "To Be or Not to Be").
Dr. Kristin Westphalen makes use of plasma torpedoes to create a thermal vent, thus relieving tectonic and magma pressure, much to the consternation of UEO Command (DSV: "Greed for a Pirate's Dream").