De Loco (デ・ロッコ De Rokko ) is the mentally unstable head of the Valuan Armada's Research and Development Division, as well as the Fifth Admiral. Vyse and De Loco face off against each other a multitude of times, with three direct confrontations over the course of the game. His ship is called the Chameleon.
Short in stature and prone to deranged monologues whenever the mood takes him, De Loco is the head of the Valuan Armada's weapons development department. His body is enclosed within a machine which appears to be a form of environmental suit, complete with breathing apparatus for his encapsulated head. Exactly what caused De Loco to don this unusual attire is not explained.
De Loco is very confident in his research, battle weaponry, and strategy. When the results turn against him however, De Loco will scream and panic in a frenzy, wondering how he could have gotten those results before he spontaneously freezes up and faints, at which point his vice captain attempts to shake him back to consciousness. This becomes a running gag as Vyse encounters De Loco, being subverted only in De Loco's final stand against Vyse in the Vortex which leads to his death.
De Loco searches for the Green Moon Crystal in Ixa'Taka by burning the entire rain forest to the ground. Vyse confronts him immediately and is triumphant in ship to ship combat, after which De Loco vows to make him "die slowly." Soon afterward, Vyse finds himself within De Loco's home turf; Moonstone Mountain, the Valuan headquarters in the region. Despite De Loco's twisted plans he fails yet again, as the traps he had intended to kill Vyse with (as well as every other machine within the base Centime could get his wrench at) are all disabled by the rescued Blue Rogue. De Loco is enraged to the point of comedy, at which point he passes out.
Then the King of Ixa'Taka awakens Grendel in a desperate attempt to take on the Valuans himself. Alfonso quickly flees the battle but De Loco calmly attacks the king's ship and knocks him unconscious. Without a master the Gigas goes into a frenzy, while De Loco gleefully watches knowing that Vyse would come to try and stop it and give him another chance at revenge. Very soon afterward, De Loco challenges Vyse to another ship-to-ship battle, this time using his most powerful experimental weapon, a prototype-Moonstone Cannon. The battle is another rout for Vyse and De Loco is forced into a humiliating retreat back to Valua.
Later in the game, Galcian summoned all the admirals to Dangral Island and revealed his plans for the armada to secede from Valua and take the world for himself. De Loco chose to side with Galcian, to continue his research and for another chance at killing Vyse. He was next seen showing Galcian the modification to the Chameleon which would allow him to enter Deep Sky where Soltis was.
The third and final encounter occurs in Deep Sky while Vyse and crew attempt to recover Fina's ship. De Loco, now hell-bent on getting revenge and destroying Vyse for good, ambushes the Delphinus upon the return ascent from Deep Sky. He unleashes his newest weapon, the De Loco harpoon cannon, vowing that he will defeat Vyse just as Vyse had defeated him in Ixa'Taka with a Harpoon Cannon. Unfortunately the De Loco Harpoon Cannon turns out to be a complete bust, as it actually enables the Delphinus' cannons to hit his ship.
De Loco's final attempt to extract vengeance on Vyse ends horribly for him. His newest advanced weapon is not enough to defeat Vyse's own ship, the Delphinus, and the Chameleon is destroyed as a result. As the Chameleon, finally beaten beyond all limits, sinks to the bottom of Deep Sky, De Loco completely loses all sanity, and is last seen screaming, flailing, and cursing at Vyse as the flames of his own destruction close in around him. Before the Chameleon sinks to the mud below, a critical system fails within the ship and the vessel explodes with extreme force, killing De Loco and all hands aboard.
- De Loco's name literally translates to "Of Crazy" in Spanish. It is appropriately fitting, given his propensity to explode in maniacal rants and raves when his plans fail.
- De Loco makes a possible reference to "Impossible Mission" for the Commodore 64. He partially quotes an iconic statement from Impossible Mission's evil genius Professor Elvin Atombender when Dr Loco says "I've prepared my favorite room just for you... Please, come in and stay awhile... Stay forever!!! Hehehehe!"
- Aside from Ramirez, De Loco is the only one of the Admirals to be killed by Vyse.