According to reports, some of these objects travel at extraordinary speeds below the surface and appear capable of transitioning seamlessly between air and water without a significant splash, shockwave, or debris trail, behavior that challenges known engineering limits. 

Navy witnesses have claimed to observe massive craft, allegedly comparable in size to a football field, moving at hundreds of miles per hour underwater, performance far beyond publicly acknowledged human technology. 

Skeptics argue these sightings could involve advanced drones, sensor anomalies, or classified military projects. Others speculate about more unconventional explanations, ranging from unknown marine phenomena to non-human intelligence, including extraterrestrial or hypothetical deep-ocean civilizations. 

Beyond military encounters, civilians have also reported unusual underwater sightings. In 2002, a deep-sea diver filming a squid at a depth of 421 meters reportedly captured footage of a fast-moving unidentified object, an incident some interpret as a possible USO encounter.