The strange device was identified as a US-made EARS (Environmental Acoustic Recording System), an underwater microphone capable of recording sounds on the ocean floor for up to an entire year.
A Croatian fishing boat has pulled up a US Navy underwater recording device from the depths of the Adriatic Sea, an arm of the Mediterranean separating the Italian Peninsula from the Balkan Peninsula, according to Alugy.com.
The strange device, recognised as an EARS audio surveillance system, was said to have been placed there by the US Navy to record local undersea sounds to document the normal audio environment in that area in order to distinguish unfamiliar sounds.
The fishing boat reportedly caught the 220-pound device while it was trawling in 460 feet of water near the island of Mljet on 6 January. The fisherman had no idea what the package was but decided to take it with him.
Following the spread of photos showing the unfamiliar object on social media, the US Navy reached out to the owner of the trawler, and asked for the device to be returned, reportedly paying the fisherman some $3,000 for the damage it caused to his nets. The recording system was reportedly then handed over to a US Navy oceanographic survey ship.
The purpose behind the US Navy’s EARS technology to record underwater sounds in the Adriatic Sea is believed to be either monitoring and identifying submarine activity in the area, or learning how to allow US Navy submarines to blend in with the ambient noise of the region, according to a naval expert, cited by Popular Mechanics.