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 serpentine Gunmen fortress, which served as Adiane's flagship. Little is known about its abilities, other than its obvious aptitude for sea travel. 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 either divert or even create large volumes of water). 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. Its main weaponry consisted of torpedoes guided by dolphin Beastmen and two massive pincers, which it used on its attempt to drag the Dai-Gurren to the bottom of the ocean. After bringing the Dai-Gurren back to the surface, the Gurren-Lagann obliterated the Dai-Gunkai completely, but Viral, who was commanding the ship at that time, managed to survive.

The "kai" in the name can be translated as "sea", referring to it being an ocean-based unit.

Movie Version
In the movie, it has a slight redesign. This was likely done for the land combat it would be partaking in. It has more defined and larger lower section than the Tv show version and could defeat Dai-Gurren in a wrestle of brute force.