The TIE Fighter Boat, sometimes referred to as the TIE Sub Fighter, is an aquatic superiority fighter version of the original TIE Fighter model. This particular TIE has been designed exclusively to operate underwater. Normally attached to Imperial Army Aquatic Garrisons, the TIE Fighter Boats serve as underwater patrol and defense craft. They can also work together with Aquatic Terrain Armored Transport Swimmers (AT-AT Swimmers) and Aquatic Assault Stormtroopers (Seatroopers) in deep water assaults.
Since the The TIE Fighter Boat can't operate in space or in normal planetary atmospheres, the Imperial Starfleet doesn't have as many of these craft at there disposal, as the Imperial Army. But if needed in special missions, Naval Command will supply the ships along with other aquatic assault vessels. The Imperial designed AT Barge, onboard most Imperial Star Destroyers and heavy cruisers, is also used to deploy the AT-AT Swimmers and TIE Subs directly into the oceans.
The TIE Fighter Boat is armed with an underwater blaster cannon and 6 underwater missiles with the blast effect of standard space concussion missiles.