The whole Ballard titanic story thing is closely related to the Thesher. He was being funded by the navy to find the thresher under the cover of searching for the titanic. Ballard convinced them to allow him to use some of the time, provided he found the thresher, to Actually look for the titanic.

nformation declassified in the 2008 National Geographic Documentary Titanic: Ballard’s Secret Mission shows that USNR Commander (Dr.) Robert Ballard, the oceanographer credited with locating the wreck of RMS Titanic, was sent by the Navy on a mission under cover of the search for Titanic to map and collect visual data on the wrecks of both Thresher and USS Scorpion.[30] Ballard had approached the Navy in 1982 for funding to find Titanic with his new deep-diving robot submersible. The Navy conditionally granted him the funds if the submarine wrecks were surveyed before Titanic. Ballard’s robotic survey showed that the depth at which Thresher had sunk caused implosion and total destruction; the only recoverable piece was a foot of mangled pipe.[31] His 1985 search for Scorpion revealed a large debris field “as though it had been put through a shredding machine”. His obligation to inspect the wrecks completed, and with the radioactive threat from both established as small, Ballard then searched for Titanic. Financial limitations allowed him 12 days to search, and the debris-field search technique he had used for the two submarines was applied to locate Titanic.[32]

https://en.m.wikipedia.org/wiki/USS_Thresher_(SSN-593)