Jagged Deep is the third Black Box collectable in Horizon Forbidden West.
Transcript[]
SECOND OFFICER BASSILI: I can't raise the airfield. Must've been destroyed.
CAPTAIN VEESENMEYER: Well, we're out of time and out of fuel. I have to put us down on that lake. Let's give these soldiers a chance to die fighting.
SECOND OFFICER BASSILI: This is the flight deck. We're going for a water landing. Leave everything behind except what you need for the fight. Now's your time to go out in a blaze of glory. Brace, brace!
Location[]
Found underwater of the Jagged Deep Delve among the aircraft wreckage.