Impostor Captain Tennille

Captain Tennille's impostor, officially known as Impostor Captain Tennille (偽キャプテン・テニール), is an enemy Stand user appearing in Stardust Crusaders.

He accosts Jotaro and his group aboard a ship they take from Hong Kong to Singapore.

Appearance
The impostor appears as a tall, muscular man possibly in his late thirties.

Though the reader is never shown the true Captain Tennille, one can assume that he was practically identical to the impostor, since his men, who had worked for ten years on the same ship, did not even suspect the replacement.

Personality
The impostor appears to be very patient, as he originally planned to separate the protagonists and kill them one by one. Once his schemes are spoiled by Jotaro, he does not lose his calm, saying that it will be no problem for him to kill them all at once from underwater. He also enjoys guessing what his enemies are thinking.

He also seems to be fond of the ocean, being rude towards Jotaro after seeing he was smoking and asking if he was going to throw the ashes and the cigar in the water (although this clashes with the fact that he disposed the real Captain Tennille's body by throwing it into the ocean).

Abilities
The impostor's Stand is Dark Blue Moon; a considerably independent humanoid Stand of great advantage in water.

The Impostor's lung capacity surpasses human average by three times, and through practice, he can stay underwater for more than six minutes without breathing.

History
The impostor is one of the Tarot Card representatives sent by Enya the Hag to kill the Joestar group. Seeing that the Joestar group decided to travel by sea after the attack of Gray Fly and how the captain of the ship looks just like him, he decides to kill the captain and take his place. He throws the captain into the ocean and boards the ship with everyone else, no one noticing that he isn't the real Tennille. He plans to kill the group one by one while inside the ship.

Stardust Crusaders
The imposter appears on a boat that Jotaro Kujo and company have taken to go from Hong Kong to Singapore. After Jotaro and Anne are attacked in the water by a mysterious creature, Jotaro has become suspicious of the crew members and believes one of them may be a Stand user.

Although Joseph Joestar insists that the Speedwagon Foundation had checked his credentials, Jotaro decides to find out if he is the culprit anyway by playing a bluff on him: he says that breathing even a minimal quantity of smoke causes a big vein to appear on the nose of a Stand user. Captain Tennille immediately falls for it, and reveals that he is actually an impostor of the real Captain Tennille, who he had killed earlier in Hong Kong bay.

He tries to take Anne hostage, but before he manages to do so he is stopped by Star Platinum. The Impostor, however, drags Jotaro underwater with his Stand Dark Blue Moon, where his Stand can fight at full power. He traps Jotaro into a vortex, attempting to slash him with Dark Blue Moon's razor scales. He even manages to create some sort of little Cirripede-Stands that drain energy from his opponents' Stands.

Finally, by exploiting Star Platinum's ability to stretch his index and middle fingers, Jotaro stabs the enemy Stand and rips half of his head, defeating him, but in a last ditch effort, Captain Tennille blows up the ship, leaving the protagonists to meet their next Stand encounter, Strength. Tennille, however, is left to die in the sea.

JoJo RPG (SFC)
The events from Dark Blue Moon occur on some different ways from the original story, as Impostor Captain Tennille uses his Stand to attack the party within a water trap found in a building. Also, Anne is completely removed from the game, resulting in Impostor Captain Tennille not using her as a hostage to attack the team.

Heritage for the Future (PS1/DC/Arcade)
Unlike the previous game, the events from Dark Blue Moon appear on the game with nothing removed. It appears as a "quick time event" mini-game in Super Story mode, where the player must dodge all the attacks from Impostor Captain Tennille's Stand. The mini-game can be replayed on Gallery Mode (Oingo and Boingo's book).

Trivia

 * The impostor is the only unnamed villain from Part III whose name remained never revealed in supplementary merchandises, and he is still only known as "The Impostor Captain Tennille".
 * Even though he doesn't appear in the OVAs, the method used to reveal his identity as a Stand user in the manga is used for a different enemy: Enya the Hag.
 * In the US licensed adaptation of the anime on CrunchyRoll, Impostor Captain Tennille is renamed Captain Dragon. This name change actually still ties into The Captain & Tennille reference, as The Captain's real name is Daryl Dragon.