The Rorkal is William's personal Nav Skid, created for him by X.A.N.A.. It has extra fins and is less sleek and hydrodynamic than the other Nav Skids. Unlike the Lyoko Warriors Nav Skids, the Rorkal is stand-alone and does not attach to the Skidbladnir.
Its weapons are torpedoes, like the other Nav Skids, due to the data used to create it being stolen from the Skid itself in The Lake. Its speed however, is unknown, as it sometimes seems to have no trouble catching up with the Lyoko Warriors' Nav Skids, while other times it can lose track of the Nav Skids, especially when they use sharp turns.
Like the Warriors with their Nav Skids, X.A.N.A. William uses his eye to aim for the desired target, then fire missiles by pressing the buttons on the control sticks. The Rorkal was presumably destroyed by the X.A.N.A. destruction program in Fight to the Finish. Its name comes from the French word for "whale;" "rorqual."