The mystery object was handed over to the crew of the US Naval Service's Oceanographic survey ship USNS Bruce C. Heezen. H I Sutton (Author)
Forbes: Mystery Underwater Device Lost By U.S. Navy
A Croatian fishing vessel netted more than it bargained for when it pulled part of a U.S. underwater system out of the Adriatic on Jan. 6. The Marian II was trawling at depths of 460 feet when the snared the mystery object. The device, weighing about 220 pounds, was hauled up onto deck. The crew, and local media could only speculate as to what it was.
The object consisted of a square orange buoy with an anchor underneath. There appears to be a Teledyne Model R12K Acoustic Transponding Release in one of two vertical tubes. This would be used for launching another more valuable instrument. The yellow tubular object appears to be a Kongsberg cNODE transponder which can act as a sophisticated beacon.
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WNU Editor: It must have been important. The US Navy moved very quickly to get it back, and probably paid a good amount of money to get it back.