There were two different tape recorders used for Phelps mission briefing. The first one with reels running is a stock Craig 222. After Phelps stops the tape a different machine is used. There are holes drilled under the take up reel where the smoke comes out.
When Thomas and Dall are pulling Kelso's unconscious body out of the lake, the actor playing Kelso climbs up the rocks to help the other actors.
Near the end as Barney (Greg Morris) struggles with Thomas O'Connel (Robert Hogan), he subdues him with a karate chop to the neck. The sound effect for this action, however, is still that of a punch thrown to the jaw.
During the teaser when one of the characters gets shot, the shadow of the boom microphone is clearly visible against the wall near the staircase, and is quickly swung out of the shot as he falls.