The Sea Fox is a customized submarine built by Rotor Walrus for Miles "Tails" Prower in 3235, as Tails had wanted a submarine ever since Rotor finished his Bathysphere submarine. It is a small, blue, grey, white, green and yellow metal submarine with torpedoes and nose drill.
While Rotor did build the Sea Fox for Tails, Tails wasn't allowed to use it properly by Princess Sally's orders as she thought him too young, and made sure Rotor didn't put any oil in the Sea Fox and would just let Tails play in it. Tails was enraged by this, but suddenly heard clapping and saw an oil-soaked seagull in the water of the dock where the Sea Fox was tied up. The seagull revealed that he had swam all the way to shore and that Dr. Robotnik had made a new undersea henchmen after rebuilding his sub-merged, waterproof robot maker that the Freedom Fighters had destroyed. The seagull demanded that Tails go after the henchmen, so Tails used the oil the seagull was covered in on the Sea Fox to make it operational, and went off on his mission. Tails quickly made his way to Robotnik's new sub-merged, waterproof robot maker and spotted Robotnik's new henchmen, Octobot guarding the entrance and capturing sea creatures to be roboticized upon his arrival. Tails attacked Octobot using the drill on the Sea Fox, causing the Octopus robot to release the sea creatures. Tails then launched a torpedo at the robot maker that caused a massive explosion, propelling the Sea Fox and Octobot to the surface of the ocean. Tails then returned home and left Octobot in the ocean, who vowed to one day return. (OSM: #1; STT)
After Sonic slapped him around while under Robotnik's control, Tails stormed off in his Sea Fox for being treated like a kid all the time. Tails's departure was noticed by Robotnik, however, via a secret camera hidden in a tree near the dock. Robotnik decided to use a leftover Auto Automaton from his recent war with Princess Sally to try and trap Tails. Meanwhile, Tails came across an uncharted island and heard a cry of "HELP!" and mistakes the robot for a real female Fox in trouble. Tails flew out of his Sea Fox and falls in love the moment he lays eyes on the robotic replica of a younger Fiona Fox. Tails then spent a romantic day together with the robot Fiona, but Robotnik then had Fiona lure Tails into a hidden Roboticizer, but Tails escaped by clogging the machine with his fur. Tails was then attacked by the Auto Automaton Fiona, but Fiona falls into the water surrounding the island and begins to rust, paralyzing her. After taking the robot Fiona out of the water and placing her on the island as a monument, Tails then began to clean up the litter Robotnik left behind, and came across a list of supplies that confirmed that Robotnik had plans for a satellite operation somewhere on the planet. At first, Tails thinks he should call Sally and tell her about it, but then thinks that the other Freedom Fighters will leave him behind again if he does. Tails then decides to prove himself by going on this mission alone and returns home to Knothole in the Sea Fox. (StH: #28, #29; PSM: #1, #2, #3)
Tails used the Sea Fox one last time to investigate a list Robotnik had dropped after Tails had his heart broken by the Auto Automaton version of Fiona Fox, which provided proof that Robotnik had plans for a satellite operation somewhere on Mobius. Deciding to keep it a secret and go his mission solo, Tails took the Sea Fox out into the Mobian Ocean and spotted a blimp filled with supplies that was using an "umbrella cloak," stopping anyone from seeing it unless they were directly underneath the blimp. Tails flew toward the blimp to and saw they were heading to Downunda, but an Aerobot blasted him with a disruptor, causing Tails to fall toward the ocean with the Aerobot in pursuit ready to destroy Tails. Tails managed to recover in the nick of time, however, with the Aerobots still hot on his heels, but Tails made a vortex using the ocean's water and his twin tails to subdue his pursuers. Tails went back to the Sea Fox to think up a new plan, but Octobot was lying in wait for him and captured him. Octobot then used his tentacles to punch two holes in the bottom of the Sea Fox, causing it to sink, and then dragged Tails underwater. But thankfully, the Plankton Intelligence Agency alerted the Forty Fathom Freedom Fighters of Octobot's doings and saved Tails before he could drown, but the Sea Fox had been left destroyed by Octobot. (StH: #28, #29; TMS: #1)
- The Sea Fox was originally a submarine introduced in the game Sonic the Hedgehog Triple Trouble, and made its final appearance in Tails' own game, Tails Adventure.