Marine Ships are ships that serve the Marines, acting as their transportation and means of fighting naval warfare. While standard Marine ships are average in size, a variant exists that is much larger, known as the Battleship (Gunkan). This ship type is the mainstay of the Marines in the Grand Line, and it is also the one used during a Buster Call. Battleships are larger than a normal-sized giant and roughly the size of the super giant Oars Jr., making the ship class among the largest in the world. These ships are used by higher-ranking Marines, such as Admirals and Vice Admirals.

Battleships have four masts, two with two sails and two with one. Like Standard ships, they have a circular superstructure from which one of the main masts emerges from, but theirs has another level. Another rectangular superstructure is affixed to the stern, which is topped by a tan tower. They have three distinctive triple-barreled guns on their front and sides, which are powerful enough to completely destroy smaller vessels and even obliterate an entire island, though only in groups. In addition to these guns, battleships possess two sets of six large cannons on both sides of their hulls.