The FISH was a scrapped C.I.A. project from the 1950s resembling a stereotypical U.F.O. It serves as a cloaking system for Warehouse 13 for all aerial detection including radar, sonar, and satellite.
It constantly projects an image of an empty lot in order to make it appear that the Warehouse doesn't exist; it requires regular maintenance in order to continue the projection.It is hidden on a mountainside several miles away from the Warehouse, invisible and inaccessible without use of the Wand/Gun seen in the pilot episode.
In "Instinct" Artie, who was the only person inside the Warehouse at the time, felt the entire Warehouse shake. In order for the FISH to cloak the Warehouse it maintains an aerial video recording of the Warehouse. Artie checked the FISH's recording of the Warehouse when he felt the Warehouse shake and his suspicions were confirmed that it wasn't an earthquake that he felt because only the Warehouse shook and not the mountain behind it. It was later discovered that the Warehouse's shaking was being caused by the Gold Spike from the Trans-Continental Railroad getting stuck in the Warehouse's expansion joints.
In "Endless Terror" Claudia hacked into the FISH so instead of hiding the Warehouse the FISH hid them from Paracelsus as Louis XIV's Silverware Forks hid their presence, but couldn't hide the aftifacts they were moving around.
Real World ConnectionEdit
After Paul Tibbets dropped the Little Boy atomic bomb on Hiroshima, the U.S. government believed that future wars would be won in a laboratory and not on the battle field. During the 1950's the U.S. military secretly funded programs all over the country that were attempting to create new methods of warfare. The military employed some of the brightest scientific minds of the era to build biological, unconventional, and chemical weapons like super soldiers that could be used to fight future wars. Some discoveries were utilized while others were scrapped and written off as failures. The files/any evidence to these top secret programs existence were destroyed and anyone who was involved in the program was forced to sign a confidentiality agreement that charged them with high treason if they so much as admitted to the project's existence.