Urquhart Bay sonar targets, Loch Ness

In 1968 the Loch Ness Phenomena Investigation Bureau wanted a new kind of evidence. Founded in 1962, the bureau persuaded Professor D. Gordon Tucker to bring his equipment to the loch. Tucker was head of electrical engineering at the University of Birmingham and an expert in sonar. He volunteered his services.

A prototype long-range sonar transducer was fixed underwater at Temple Pier, on the north side of Urquhart Bay near Drumnadrochit. It was aimed at the opposite shore. In effect, an acoustic net was strung across the loch. The cathode-ray display was photographed every 10 seconds by a movie camera. Trials ran in April and again in August 1968.

For some days, nothing of interest was seen. Then came August 28. At 4:30 in the afternoon, a remarkable 13-minute sequence began. A large object rose rapidly from the floor of the loch at a range of 0.8 kilometer.

It climbed at about 100 feet a minute, rising obliquely away from the sonar at about 6.5 knots. Soon it was 1 kilometer away, and its ascent had slowed to about 60 feet a minute. Then it changed direction and moved toward the pier at about 9 knots, keeping constant depth. Finally it plunged to the bottom at about 100 feet a minute. It rose again at 0.6 kilometer range, moved out of the beam and was lost to record.

It was not alone. A second large object had been detected 0.5 kilometer from the pier. It finally dived at 450 feet a minute. Both objects remained many feet below the surface. When the bureau later studied the oscilloscope film, it described a fast-diving object about 6 m long, followed by a whole group of such objects.

Hugh Braithwaite and Tucker published the results in New Scientist on 19 December 1968, as "Sonar picks up stirrings in Loch Ness." The Glasgow Herald covered it the next day, and TIME followed on 27 December. Several targets had been recorded over the two-week August run. One was probably a fish shoal. Others "moved in a way not typical of shoals at speeds up to 10 knots."

Tucker said the echoes were "clearly" made by animals. The rapid rise and fall, he said, made fish very unlikely. But he stopped short of claiming proof. He wanted to continue with refined equipment.

After further work on site through 1970, Tucker and D. J. Creasey published a follow-up paper in the Proceedings of the Challenger Society. A later reassessment of Loch Ness sonar searches states that Tucker attributed the earlier contacts to gas bubbles and thermal effects over the long range of the beam, some 1.2 kilometers. Ronald Binns, in The Loch Ness Mystery Solved, reads the 1970 paper the same way. An article in The Skeptic pointed to strong refraction of sound in the thermocline.

Not everyone closed the file. In 1983 the Loch Ness & Morar Project, Adrian Shine's group, reported that its own repeatable sonar contacts seemed to confirm those of other expeditions, particularly Birmingham University in 1968.

No one saw a creature. No photograph shows one. What survives is a scientific paper, a handful of press reports and a film of an oscilloscope screen that has never been traced online. Yet the Temple Pier trial remains a reference point for the sonar searches that followed, from Robert Rines in 1972 to Operation Deepscan in 1987 and a BBC survey in 2003.