5. USS Cyclops
The Cyclops was a massive steel-hulled fuel ship owned by the US and tasked to transport coal and other important supplies for the US Navy. On her final journey, the boat left Rio de Janeiro’s harbor having about 300 people on board along with a full load of over 10,000 tons of manganese ore.
The Cyclops was last seen in March 1918, when it sailed away from Barbados going towards what we now call the Bermuda Triangle. It appears that the ship has vanished without a trace, and the incident has been seen deemed especially mysterious as no one made any distress call and no severe weather was reported in the area.
Theories — some more inventive than others — began to surface that the Cyclops had been sunk by a German boat, been the victim of a violent mutiny, or attacked by a giant octopus or squid. A massive search for the ship was launched with several boats and planes scanning the whole area for survivors and debris, but the enormous ship was never found.
If you liked this article, you may also find this one interesting: 10 Planes That Disappeared Without A Trace.