The Eldridge was part of the 'Philadelphia Experiment', which tried to make the ship invisible. Instead, the project bent the laws of time and space, causing the ship to travel through time. The crew members who didn't die were driven insane. The USS government tried to stop the project, but were thwarted when the ship fell through a dimensional rift and ended up on the sea floor. (AUDIO: The Macros)
The ship vanished, reappearing underwater near the former site of submerged London in the 23rd century. It let loose a blast of vortron energy, which poisoned people on the nearby underwater base Poseidon 8. The ship had left a dimensional vortex open, bringing the Vashta Nerada and an alien shark through the gateway. The Eleventh Doctor concocted a cure for the vortron radiation poisoning and closed the gateway. (GAME: Shadows of the Vashta Nerada)
Behind the Scenes
- An urban legend regarding the USS Eldridge purports that during wartime, experiments did take place there involving invisibility and teleportation.