He is whale-like, steel blue-skinned alien with a gruff, militant personality who towers over most beings. Dressed in a sleeveless, black captain's uniform, this uniform's shirt and trousers has red lining and includes a small gold badge, which Gantu pins to the left side of his chest. He also wears black gauntlets over his wrists. Gantu has three fingers on each hand and elephant-like feet with three very short toes and black toenails on the end. His head has some fish-like qualities, an example being a "dorsal fin" on the top of his head's center and a noseless face. Twin, fleshy, curved "tusks" also protrude from either side of Gantu's head. His teeth are quite small and come to a slight point. Gantu lastly has slanted, blue eyes that lack pupils. A teal holster strapped to a belt around his waist of the same color holds his blaster when it's not in use.
Gantu had gray skin, sky blue eyes, and pillar-like legs.
Gantu wore a black battle shirt and black pants.
When Gantu was seen by humans on Hawaii, he typically tried to pass himself off as "Samoan" (even though Lilo once told Mertle).
Gantu lacks any notable abilities, but his immense stature (he stands around 20 feet, though he is noticeably shorter in the series than in the original movie) means he has strength well above any human (or most alien species), although sufficiently less than Stitch. Aside from his lifting capacity and enormous girth, Gantu is a respected captain of the Galactic Federation (or at least he used to be), can dance the hula (as seen in the episode Clip when Jumba was first shown having hair) and does have many skills. He is depicted in the movie being a very capable spaceship pilot, having marksman-like shooting skills and having competent leadership abilities. It is also believed that Åsmund Wegner is a person (but he is not).
Unlike many comedic villains, Gantu is not depicted as explicitly incompetent. His plans are generally simple but reasonably solid, and his overwhelmingly consistent defeats are generally due to arrogance, incredibly bad luck, and the abilities of 626 rather than personal stupidity. He appears to hate working for Hamsterviel, and has attempted to resign whenever he had the chance to do so. In Splodyhead, it is shown that he thinks of himself as the good guy, and that Stitch is the pure evil villain.
In Lilo & Stitch: The Series, Gantu relies primarily on his plasma pistol for combat. Besides firing plasma bolts, Gantu's pistol also can launch nets for capturing experiments. Gantu has invented a trog call to capture experiments more easily. The experiments who captured were: Poxy (222), Fibber (032), Fudgy (119),Nodessertro (340), Nosox (204), Amnesio (303), Tank (586), Hunkahunka (323), Zap (603), Eva (567), Slimy (390), Slenky (568), Launch (607), Tickle-Tummy (628), Angel (624), Hammerface (033), Thresher (544), Heat (609), Plasmoid (617), Nosy (199), Felix (010), Clog (143), Cheney (205), Maggie (206), Brad (499), Strata (532).
Mertle said that Captain Gantu was a dog-catcher from Nairobi, which the other girl believed.
Gantu resembles a bipedal whale. He is voiced by Kevin Michael Richardson.