Jack's not wholly oblivious, but he's busy with the controls and doesn't give it a proper look for another few secoNDS HOLY SHIT THAT'S A TORPEDO

Seriously, you don't need military training to recognise a torpedo, it's big and metal and murder-shaped and it's heading straight for the bathysphere.

With a shout of alarm, but without any more warning than that, Jack takes evasive action. He yanks with all his strength at two of the joysticks, spinning the bathy out of the way. In the next heartbeat, the torpedo goes past so close that they can hear the angry pinging of its sonar.