The Captain Tennille Imposter is the stand user of Dark Blue Moon.
The Captain Tennille Imposter was sent to Hong Kong by Enya Geil in order to kill Jotaro and his group. He then killed the real captain Tennille, who looked similar to him, planted explosives on the boat and waited for the group to arrive.
The Captain Tennille Imposter was created by Hirohiko Araki, the author and illustrator of series, as a major character of Jojo's Bizarre Adventure's third arc, Stardust Crusaders. His identity is based on the American musical duo Captain & Tennille.
He is a tall, muscular man with yellowish hair. While trying to impersonate Captain Tennille, he wears a skin tight blue shirt, a red cloth around his neck, two white gloves with black bands, a pair of white pants and a ship captains hat. When his true identity was revealed, his pupils shrink and both eyes roll upwards slightly.
The imposter is man who keeps his calm disposition while fighting his opponents and constantly guesses their thoughts. He is also somewhat careful for having a backup plan in case he was defeated.
The imposter uses his Stand Dark Blue Moon to attack Jotaro while he was trying to save the runaway girl Ann. After the group begins to settle down, the imposter appears while under the guise of Captain Tennille in order to subdue Ann for being a stowaway. However, Jotaro soon accuses him of being the Stand user after he puts out his cigarette. He then falls for Jotaro's trick and reveals himself to be an imposter. He then captures Ann and tries to jump into the ocean but Jotaro attacks and seemingly defeats him before he could fall in. However, it is revealed that he used Jotaro's attack as an opportunity to create and plant acorn barnacles onto him. The barnacles then begin to drain Star Platinum's strength which causes Jotaro to plummet into the water. The imposter then creates a whirlpool in order to trap Jotaro and cut him with Dark Blue Moon's razor sharp scales. Before he could deliver the final blow, Jotaro concentrates the remainder of Star Platinum's power into its index fingers and rips off half of Dark Blue Moon's and the imposter's head. Before he dies, the imposter sets off the explosion he planted on the ship in order to slow them down.
Dark Blue Moon
A blue, humanoid Stand with a flat head, four yellow eyes, fins, webbed appendages and jaws. It also has scales covering some parts of its body.