I could be wrong ... but I think you are trying to do the same thing I did. The door you may be trying could be the under water caves door which opens a bit later AFTER you do the gunnery range. The gunnery range door auto opens after you jerry rig the wires. So the door should be open, then you do Ops training THEN the door you could be screwing with will open up.Sorry if I'm totally off here rambling.
L8er,
Eric