Case file · Unidentified submerged object

Puerto Rico Trench USOs

Naval exercises off Puerto Rico logged a fast underwater object ('the Quasimodo') outrunning the fleet.

1963 CE · 19.80, -66.50 · status: account

The sceptical view

Based on sailors' accounts and unreleased sonar; unverified.

A naval legend with no released data. Sonar artefacts, sea life and secret submarines explain such contacts far more often than unknown craft.

Explanation	Weight	Why
Something known, misidentified	34%	Deep sonar contacts are often whales, fish schools or a ship’s own echoes; untrained retellings turn ambiguous returns into a fast craft.
Secret human technology	18%	Cold War submarines, torpedoes and test vehicles of both blocs operated in the Caribbean; an unexpected friendly or Soviet contact would be kept quiet.
A known natural phenomenon	14%	Sound in the sea bends through thermoclines and the deep sound channel, so ranges, depths and speeds read from sonar can be badly wrong.
A hoax or fabrication	12%	The story cannot be traced to a named log or witness and circulates in popular books; it may be embellished folklore.
Genuinely anomalous	12%	If the claimed speed and depth were real they would exceed any 1963 submarine, but nothing has been released to check.
Perception, memory or mind	6%	Sailors retelling an old exercise contact years later will sharpen it.
A poorly understood natural phenomenon	4%	Poorly understood ocean acoustics could produce a phantom target.

Official position: No official statement; the US Navy has released no sonar records of the event.