Dai-Gunkai

The Dai-Gunkai (ダイガンカイ, Daigankai?), rivaling the Dai-Gunzan in terms of sheer bulk and apparently much lengthier, is an aquatic Gunmen fortress resembling a centipede, which served as Adiane's flagship. The primary utility of the vessel is its aptitude for sea travel.

Appearance
The Dai-Gunkai resembles a massive centipede or some other kind of worm, with a long body and many small "legs" (actually fins) lining its sides. The bow of the vessel is shaped like a grinning face with eight eyes and a pair of scythe-like pincers. The bridge resembles that of a submarine, but is decorated with four eyes and has functional segmented arms with huge lobster-like claws.

Role in the show
The only appearance of the Dai-Gunkai in combat was in Episode 12, when it ambushed the Dai-Gurren while it was crossing the ocean on its march to the Helix Empire's capital. As Dai-Gurren futilely attempted to attack the submerged ship, Adiane gave command to Viral, having decided to personally confront the humans in her Sayrune.

With Adiane running interference, Viral sent Dai-Gunkai to cut off Dai-Gurren's flippers, before grabbing it from below and attempting to drag it underwater. The scheme was thwarted, however, by Gurren Lagann, who escaped Adiane and used a drill like a waterscrew to push Dai-Gurren back to the surface, ripping off Dai-Gunkai's claws in the process. After bringing the Dai-Gurren back to the surface, the Gurren-Lagann obliterated the Dai-Gunkai by drilling through its entire body, with Viral as the only survivor.

Weaponry and capacities
While it seems to only be able to travel in a body of water, the Dai-Gunkai's first appearance was marked by a sudden deluge over the battlefield, suggesting that it may have the ability to divert - or even create - large volumes of water. Like a submarine, the vessel can travel deep underwater and withstand crushing pressure. The maneuverability and the power of the Dai-Gunkai underwater are impressive, as it is able to easily pull the Dai-Gurren deep down into the ocean.

Its main weaponry consisted of torpedoes guided by dolphin Beastmen and two massive pincers, which could tear even the Dai-Gurren's hull. It also possessed a cannon in each eye, which were apparently for surface combat.

Movie Version
In the movie, it has a slight redesign-likely done for the land combat it would be partaking in. The movie version has a saurian body with massive legs able to travel on land, with the centipede sections forming the head, neck and tail of the mecha. It could defeat Dai-Gurren in a wrestle of brute force. It eventually combined with the other Dai-Guns to create Do-Ten-Kai-Zan, but was quickly destroyed by Team Dai-Gurren.

Trivia

 * The "kai" in the name can be translated as "sea", referring to it being an ocean-based unit.
 * Along with its affiliation to the sea, the crewmen are also sea-based aquatic creatures.