During the First World War, the USS Cyclops was sent to Brazil to fuel British ships in the South Atlantic. Returning from Rio de Janeiro, she made a brief stop at the island of Barbados, then departed for Baltimore on the 4th of March, 1918. From that time forward, no one saw or heard anything about the Cyclops ever again. The crew and all 306 passengers vanished once and for all, and no trace of them or the ship has ever been found.
It remains the single largest non-combat loss of life in U.S. Naval history. Even though American Naval authorities have tried for years to give a logical explanation, the disappearance remains an absolute mystery