Summer of 1987, North Sea - Submerged Off the Coast of Newcastle

Did the U.S. Naval Academy know about this? How about Monty Python?

U.S. navy submarine detects mystery biologic noise at 170 meters during the Cold War. For about 6 minutes gurgling and faintly bleating noises were recorded on ultrasensitive equipment. Copies were soon on their way to Virginia, Northwood and Upsala.

Analysts were mystified at first. Margaret Thatcher was supposedly briefed.

Of the submarine's crew, only the CO would later learn what had actually baffled his sonar suite during the Cold War. The question is, did he believe it?

Now, 21 years later, the truth has been revealed: 6 February 2008 - The Ministry of Defence says it will abandon deep-diving experiments which involve inducing decompression sickness in live goats.

... Goats were used because their respiratory physiology is said to closely resemble that of humans. ... Animal rights campaigners say the move will 'end decades of animal suffering'. ... The animals were used to see what the likely risk of "the bends" would be following escape from a submarine at varying depths under water. The MoD said it only conducted animal testing "where absolutely necessary" and all work
involving animals is carried out in strict accordance with the requirements of the Animals (Scientific Procedures) Act 1986.

Some countries, RN divers suggest, conducted related experiments on actual humans. Wonder who that would be?

Submarines are always silent and strange.