Haven't watched the video yet, but I've heard that a submarine was dispatched to find both the Thresher, and the Scorpion, and on it's way home, that submarine took a detour and was the one that initially found the Titanic by using the knowledge of debris fields acquired in finding those 2 subs.
Bob Ballard admitted that the Titanic was just a cover story, to go looking for the submarines. They were found quite quickly and that left a couple of weeks to go and actually hunt for the Titanic. Supposedly, it was the debris field that both submarine wrecks left that gave Ballard the idea to hunt for the debris field of the Titanic, this would ultimately lead to the discovery of the wreck. They used a ROV ( remotely operated vehicle ) to go down to the wrecks, which was what interested the navy in financing the hunt. Ballard and his team also later found the wrecks of HMS Hood and the Bismark.
