Visible crew/equipment: When the Red October sub has surfaced to let the crew get off because of the supposed nuclear leak, there is a brief shot where you can clearly see the camera and its filming crew in their tennis shoes on the deck. (01:45:52)
Visible crew/equipment: When Jones the Sonar operator detects the Red October for the final time via his headphones, he is talking to someone next to him. The whole time he is doing this, a microphone boom is constantly bobbing into view from above his head.
Visible crew/equipment: In the scene where Ryan is being flown out to the Dallas, the door crew member looks out and says, "Yo, got a sub about 2 miles out." If you look closely in his goggles, you can see the reflection of the crew. (01:45:30)
Visible crew/equipment: On the Dallas, the two men are listening to sonar and get a fax that the Soviet sub is a new type. The camera moves in on the man (Jones) on the left seat and its shadow is very visible on his seat.
Answer: The trench is too deep to recover anything from the bottom of the trench. They were going to fake destroying the Red October, so they need some way to explain the lack of evidence of its destruction (because the remains were on the bottom of this deep trench).
Bruce Minnick