A lot of mystery surrounds the wreck at Zabargad Island. The best reference located is Peter Collings, who has done a lot of research on the wreck in the Red Sea and with so many different "stories", his collected data gives the most coherent story and history of the wreck.
The "fishing trawler" fleet were a common sighting from the sixities onwards in all international coastal waters around the world. The US and NATO tended to build large listening dishes with high end equipment, costing a lot of money to build and maintain. The Soviet Union had the same desire, but not the finance or capability to replicate these types of listening stations. A cheap alternative was needed. The build / bought smaller ships and converted them to floating listening stations with various antennae and sonar systems. Staying in international waters, the listened into all broadcasts, documented the information and send the information on to Moscow. During the cold war, the Soviets were based in Yemen on Socotra Island, allowing them to monitor all shipping in the Red Sea, so there is no suprise that a "spy trawler" was located in the Southern Red Sea.
Based on the published Russian Naval Fleet, the ship has many close features with the 861 MOMA class (converted). No exact numbers are published on how many were build, but they still have 6 in active service today and the layout is very similar to the shipwreck at Zabargad Island. The majority of ships were build in Gdansk, Poland between 1967 and 1974. The ships were appox. 70 to 75m in length by 11m wide, equipped with two Diesel Engines capable of about 15 knots.
On one the dive trips, a retired Naval Intelligence Officer explained some of the challenges with these boats. The antennae require huge amount of "clean" power, usually provided from a large bank of batteries held in the hold of the ship. A ship of that size, especially with DF (Directional Finding) Array, the HF Anntenna, plus the mirad of mushroom antennae found on the ship, he reckons somewhere between 200 to 300 large batteries. The Russians used lead batteries with distilled water, which have the side effect of gasing and releasing Hydrogen. The area requires constant venting during the charging process and must be kept clear of sparks and other open fires.
There is no evidence or proof that this is the cause of her demise, but something caused an explosion, causing it to break in two and sink. What evidence can be found inside? There are racks inside which clearly would have held electronic equipment with cables running all over the ship. Very telling is that no equipment can be found, hastily removed after her sinking to erase us much of her actual capabilities as possible. A more detailed report on her can be found on www.deeplens.com.