Listening beneath the waves
During World War One, almost 4,000 officers and men were trained at the Navy's hydrophone research base in Fife but there are few signs of the ground-breaking work carried out there.
The bases of a few huts and an old stone pier are all that remains of the Royal Navy base at Hawkcraig Point near Aberdour in Fife.
Back in 1915, there would have been 16 wooden huts of various sizes housing hundreds of naval personnel undergoing training in a new underwater listening device called the hydrophone.
"They were desperately trying to find a solution for the German submarine menace," says historian Eric Graham.
Hydrophones were placed at either side of the entrance to the Firth of Forth to detect submarines in what was the most strategic stretch of water next to Scapa Flow off Orkney.
Mr Graham says that the "new science" developed at Aberdour finally offered "some option of finding and tracking down who is lurking out there in 200ft of water, waiting to sink your capital ships trying to get out of the Firth of Forth".
The hydrophones were a pretty simple concept.
In its most basic form, it was a microphone in a waterproof casing extended through the bottom of the vessel.
By rotating the microphone, the sound operator was able to listen for propeller and machinery noises that might indicate the presence of a submarine.
The development of the technology started in January 1915 at Granton on the south side of the Firth of Forth.
The man behind the project was Commander Ryan, who was described as a "fractious Irishman who didn't tolerate fools".
Before long, the main hydrophone testing moved to the Fife side and was conducted from a deep-sea drifter, a large variety of fishing vessel.
The base which was set up at Hawkcraig Point took the name of the drifter and became known as HMS Tarlair.
By the end of the war HMS Tarlair numbered almost 800 personnel.
Almost 4,000 officers and men were trained at the base and 1,500 ships were supplied with hydrophones.
In a book called Hush, published in 1920, an author named HW Wilson tells of his experiences at Tarlair.
He describes the hydrophone as a microphone "enclosed between diaphragms which pulsate or vibrate" and the varying resistance can be translated in to engine sounds of ships in the vicinity.
It will also detect any "neighbouring subaqueous tremors", he says, "such as the sighs of a lovesick mermaid".
The "medley of sound" reproduced in the receiver ear is left to the judgment of the listener to classify, he says.
Wilson is scathing of the method used to select personnel for this "listening" assignment.
He says the men were subject to a rigorous medical examination but hearing was not tested.
Wilson says: "All the organic equipment with which man is born into this world, including the vermiform appendix, was scrutinized and tested. Everything came under a punishing medical survey except only the hearing."
He says any minor maladies meant naval ratings were sent elsewhere but anything short of total deafness was gratefully accepted.
Historian Eric Graham says the hydrophone had a "qualified success".
He says: "The number of actual u-boats sunk directly from a hydrophone contact are probably only three or four but you have got to imagine, that once it has been heard and got away, the whole station is on alert that there is a submarine in this area.
"It may be a week later that they make the next contact with it. So that from that point of view. It is a key device against a submarine."