Strange but true.
Yeah... I have no proof to offer.... only my word that what I describe actually did happen and I was present and, to this day, I wonder what the heck our equipment detected.
Approximately 600 miles south southwest of Oahu, steaming at 15 knots. Seas calm, no other surface vessels present according to our radars.
Around 3 am (okay.... 0300 hours) and I am one of 2 people standing watch in the sonar shack. We were inactive.... not "pinging," in the "listen mode" where we only monitor the sounds already present in the water.
One of our units provided a visual representation of the ambient sound on slowly-moving paper. The paper display was more sensitive than what showed up on the CRT display and would often show sounds we could not pick out from other ambient noises we could hear through the headsets or the speakers mounted on the bulkheads.
I noticed an odd printout on the paper and began investigating it. The other sonar tech began processing the odd noise using other equipment. Due to the "oddness" of the sound we flipped on the recorder.
We used every piece of equipment and software program available to us. The noise was definitely not natural.... not a biological source. We requested the bridge to stop the ship's engines to increase the sensitivity of our instruments. They agreed to our unusual request. Oh, those were the Cold War years and the Rooskies were definite enemies. As the ship slowed to a stop and the engines and steam turbines throttled back we garnered more data.
Describing the contact the officer of the deck granted us permission to go active, to "ping" and gather the data that method would offer. The request was seldom asked for or granted since we wanted to minimize the amount of data that Rooskies could gather about our sonar, that happened to be the latest & greatest stuff afloat a surface ship at that time.
Cranking up the critter we outputted over 200,000 watts RMS of audio power (exact amount still classified the last I heard). Immediately, every swinging **** aboard our ship was wide awake!!!! Hee hee. Loud is an understatement. You could feel the sound as much as hear it.
We correlated the info, ran it through the computers, backed it up with calculations made with pencil and paper and ran all the data again. Others checked and rechecked. There was no doubt. The contact was at least 3,000 feet below the surface and went deeper as its speed increased. We lost the contact around 7,000 feet down and it had incresed its speed to a minimum of 65 knots and our data indicated a final speed before contact was lost of 90+ knots.
At that time there was no known man-made craft capable of performing those feats. Here it is, 40 years later, and there has been NO hints of ANY human vessel capable of doing what that contact did, even with today's technology.
Our active sonar gave NO indication the contact was biological. I have tracked whales, masses of plankton, submarines etc. and none of them exhibited the properties our sensors observed or met the parameters involved. We considered the possibility it was a giant squid but the echo returns were too darn solid for a biological contact.
Our division officer took the tape, sealed it with a "top secret" label and it went into the safe. The next Navy base we entered we were met by three officers, 2 packing .45s in holsters, who signed for and carried off that tape. We never heard a word about that tape from outside sources.
The incident was hashed and rehashed by us sonar dudes. Of course we could not prove what the contact was but most agreed to the POSSIBILITY the contact MAY have been something originating from another planet. We did not give that explanation a high probability but, due to the many odd characteristices of the contact, the POSSIBILITY exists.
To this day I wonder....... what the heck was that thing?????!!!!!!!!!!!!